U.S. patent number 5,895,794 [Application Number 08/430,776] was granted by the patent office on 1999-04-20 for shelf stable cross-linked emulsions with optimum consistency and handling without the use of thickeners.
This patent grant is currently assigned to Dow Corning Corporation. Invention is credited to Daniel Trent Berg, Eric Jude Joffre, Donald Taylor Liles, Leon Andre Marteaux, Nick Evan Shephard, Andreas Thomas Franz Wolf.
United States Patent |
5,895,794 |
Berg , et al. |
April 20, 1999 |
Shelf stable cross-linked emulsions with optimum consistency and
handling without the use of thickeners
Abstract
A crosslinked polysiloxane dispersion comprising a siloxane
polymer, polymer mixture, or polymer/solvent mixture, capable of
crosslinking via condensation, addition or free radical reactions,
and having a viscosity of greater than 5000 mPa.s but less than
500,000 mPa.s, if required, 0.1 to 10 weight parts of a
crosslinking agent, and, if required, depending on the nature of
the catalyst and silicon cure system, 0.000001 to 10 weight parts
of a catalyst, 0.5 to 10 weight parts of a surfactant or surfactant
mixture, and 0.5 to 25 weight parts water per 100 weight parts
siloxane polymer. Optionally, adhesion promoters, pigments,
reinforcing or non-reinforcing fillers, silicone resins,
stabilizers, freeze/thaw additives, etc. may also be added to the
dispersion.
Inventors: |
Berg; Daniel Trent (Muskego,
WI), Liles; Donald Taylor (Midland, MI), Marteaux; Leon
Andre (Brussels, BE), Shephard; Nick Evan
(Blacksburg, VA), Wolf; Andreas Thomas Franz (Midland,
MI), Joffre; Eric Jude (Midland, MI) |
Assignee: |
Dow Corning Corporation
(Midland, MI)
|
Family
ID: |
23708975 |
Appl.
No.: |
08/430,776 |
Filed: |
April 27, 1995 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
113029 |
Aug 30, 1993 |
5438095 |
|
|
|
Current U.S.
Class: |
523/217; 523/200;
524/862; 524/837; 524/449; 524/451; 524/457; 524/779; 524/785;
524/786; 524/787; 524/788; 524/789; 524/425; 524/432; 524/435;
524/445; 524/448; 524/858; 524/863; 524/433; 524/436; 524/437;
524/441 |
Current CPC
Class: |
C08K
5/057 (20130101); C08J 3/26 (20130101); C08K
5/57 (20130101); C08K 5/098 (20130101); C08K
5/0091 (20130101); C08J 3/03 (20130101); C08K
5/0091 (20130101); C08L 83/04 (20130101); C08K
5/057 (20130101); C08L 83/04 (20130101); C08K
5/098 (20130101); C08L 83/04 (20130101); C08K
5/57 (20130101); C08L 83/04 (20130101); C08J
2383/04 (20130101) |
Current International
Class: |
C08J
3/03 (20060101); C08K 5/057 (20060101); C08J
3/02 (20060101); C08K 5/57 (20060101); C08K
5/098 (20060101); C08J 3/24 (20060101); C08J
3/26 (20060101); C08K 5/00 (20060101); C08K
009/10 (); C08J 003/02 (); C08L 083/04 () |
Field of
Search: |
;524/837,863,862,858,789,788,779,786,785,787,457,448,425,433,445,437,441,432,449
;523/200,217 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Dean; Karen A.
Attorney, Agent or Firm: Gearhart; Richard I.
Parent Case Text
This is a continuation-in-part of application Ser. No. 08/113,029
filed on Aug. 30, 1993, now U.S. Pat. No. 5,438,095.
Claims
That which is claimed is:
1. A composition comprising:
a silicone latex free of rheology modifiers having a plurality of
crosslinked polysiloxane particles, wherein said silicone latex has
at least 75% silicone content by weight, and said silicone latex
comprises
(a) a crosslinked product of (i) 100 weight parts of a siloxane
polymer or polymer mixture having a viscosity of greater than 5000
mPa.s but less than 500,000 mPa.s at 25.degree. C., and (ii) up to
20 weight parts crosslinker, the siloxane polymer or polymer
mixture having at least one polymer species of the following
Formula (I):
where n is 0, 1, 2 or 3 and z is an integer from 500 to 5000,
X is hydrogen, a vinyl group, a hydroxyl group, any condensable or
hydrolyzable group,
Y is a Si atom or a Si--(CH.sub.2).sub.m --SiR.sup.1.sub.2 group,
where m is 1 to 8,
R is individually selected from the group consisting of aliphatic
alkyl, aminoalkyl, polyaminoalkyl, epoxyalkyl, alkenyl, or aromatic
groups, and
R.sup.1 is individually selected from the group consisting of X,
aliphatic alkyl, alkenyl, and aromatic groups,
(b) 0.5 to 10 weight parts surfactant,
(c) 0.5 to 25 weight parts water, and
(d) up to 5 weight parts catalyst.
2. The composition of claim 1, wherein the siloxane polymer or
polymer mixture includes 1 to 50 weight parts of liquid, branched
methylpolysiloxane polymers comprising (CH.sub.3).sub.3 Si.sub.0.5,
(CH.sub.3).sub.2 SiO, and CH.sub.3 SiO.sub.1.5 units and containing
from 0.1 to 8% hydroxy groups.
3. The composition of claim 1, wherein the siloxane polymer or
polymer mixture includes 1 to 50 weight parts of branched
methylsiloxane polymeric resins comprising, (CH.sub.3).sub.3
S.sub.0.5, (CH.sub.3).sub.2 SiO, CH.sub.3 SiO.sub.1.5, and
SiO.sub.2 units and containing from 0.1 to 8% hydroxyl groups.
4. The composition of claim 1, wherein the crosslinked polysiloxane
particles include 1 to 10 weight parts of a compatible organic
solvent.
5. The composition of claim 1, wherein the composition includes up
to 10 weight parts filler.
6. The composition of claim 1, wherein the composition includes up
to 20 weight parts adhesion promoter.
7. The composition of claim 1, wherein the composition includes up
to 20 weight parts stabilizer.
8. The composition of claim 1, wherein the composition includes up
to 20 weight parts of a silsesquioxane resin suspension.
9. The composition of claim 1, wherein the composition includes up
to 10 weight parts of a catalyst deactivator.
10. The composition of claim 1, wherein the surfactant is present
in an amount comprising 2 to 5 weight parts.
11. The composition of claim 1, wherein the surfactant is present
in an amount comprising 0.5 to less than 3 weight parts.
12. The composition of claim 1, wherein the water is present in an
amount comprising 6 to 15 weight parts.
13. The composition of claim 1, wherein the water is present in an
amount comprising 0.5 to less than 2 weight parts.
14. The composition of claim 1, wherein the silicone latex
comprises between 80 and 92% by weight silicone polymer
content.
15. The composition of claim 1, wherein the silicone latex
comprises between 84 and 90% by weight silicone polymer
content.
16. The composition of claim 1, wherein the siloxane polymer has at
least two hydroxyl, condensable or hydrolyzable groups, the
crosslinker has, on average, at least two silicon hydrogen bonds,
and the catalyst is selected from the group consisting of noble
metal complexes, organic acid metal salts, titanic acid esters,
amino compounds and their salts, and mixtures thereof.
17. The composition of claim 1, wherein the siloxane polymer has at
least two silicon-hydrogen bonds, the composition contains a
crosslinker which has, on average, at least two hydroxyl,
condensable or hydrolyzable groups per molecule, and a condensation
catalyst selected from the group consisting of noble metal
complexes, organic acid metal salts, titanic acid esters, amino
compounds and their salts, and mixtures thereof.
18. The composition of claim 1, wherein the siloxane polymer has at
least two alkenyl groups per molecule bonded to silicon atom, and
the crosslinker has, an average of at least two silicon-bonded
hydrogen atoms, the catalyst is a noble metal catalyst, and the
crosslinker is a silicon hydride crosslinker present in a amount
sufficient to provide at least one hydrogen atom for each vinyl
group in the siloxane polymer.
19. The composition of claim 1, wherein the siloxane polymer has at
least two hydrogen-silicon bonds, the crosslinker has, on average,
at least two alkenyl groups per molecule directly attached to at
least one silicon atom, and the catalyst is a noble metal
catalyst.
20. The composition of claim 1, wherein the siloxane polymer has at
least two carboxyalkylsiloxy groups, the crosslinker is an epoxide
compound selected from the group consisting of diglycidyl ethers of
di- and bis-phenols, and the catalyst is selected from the group
consisting of (organo)metallic compounds, amino compounds, salts of
amino compounds, or mixtures thereof.
21. The composition of claim 1, wherein the siloxane polymer has at
least two hydroxysiloxy groups, and the composition further has at
least one crosslinker having on average at least two
silacycloalkane groups per molecule and a nucleophilic
catalyst.
22. The composition of claim 1, wherein the siloxane polymer has at
least two silacycloalkane groups and the composition further
includes a crosslinker having on average at least two hydroxyl
groups per molecule and a nucleophilic catalyst.
23. The composition of claim 1, wherein the siloxane polymer has at
least two silacycloalkane groups and, the composition further has a
nucleophilic catalyst, and optionally, a crosslinker having on
average at least two hydrolyzable groups per molecule.
24. The composition of claim 1, wherein the siloxane polymer has at
least two hydroxysiloxy groups, and the composition further has at
least one crosslinker having on average at least two
aza-silacycloalkane groups per molecule and a condensation
catalyst.
25. The composition of claim 1, wherein the siloxane polymer has at
least two aza-silacycloalkane groups and the composition further
includes a crosslinker having on average at least two hydroxyl
groups per molecule and a condensation catalyst.
26. The composition of claim 1, wherein the siloxane polymer has at
least two aza-silacycloalkane groups and, the composition further
has a condensation catalyst, and optionally, a crosslinker having
on average at least two hydrolyzable groups per molecule.
27. The composition of claim 1, wherein the siloxane polymer has at
least two primary or secondary aminosiloxy groups, and the
composition further contains an optional acrylating agent, and the
crosslinker contains on average at least two carboxylic anhydride
groups, and is selected from the group consisting of alkoxysilane,
alkoxysiloxane, alkoxysiloxy functional resin, alkoxysilyl
functional resin, and a siloxane containing carboxylic anhydride
groups.
28. The composition of claim 1, wherein the siloxane polymer has at
least two hydroxysiloxy or alkoxysiloxy groups, a condensation
catalyst, and a crosslinker containing on average, at least two
reactive silanol groups, and where the crosslinker is selected from
the group consisting of
a. silica,
b. silicate,
c. siliconate,
d. silanolate,
e. silanol functional silicone resins,
f. silanol functional organic resins, and
g. partial condensation products thereof.
29. The composition of claim 1, wherein the siloxane polymer is a
trimethylsiloxy or hydroxyl endblocked polydiorganosiloxane, where
the siloxane polymer contains sufficient alkenyl substituted
siloxane units to facilitate the crosslinking of a trimethylsilyl
endblocked siloxane using a peroxide or other free radical
initiator.
30. The composition of claim 1, prepared by mixing siloxane polymer
with surfactant and water, or with an aqueous solution of the
surfactant, at sufficient shear and for a sufficient period of time
to form a gel phase having at least 85% by weight silicone polymer
content, then adding, if required, crosslinker, and, if required,
catalyst, and diluting the gel phase with further water to the
minimum silicone polymer content of at least 75%.
31. The composition of claim 1, prepared by mixing siloxane polymer
and if required, crosslinker, with surfactant and water, or with an
aqueous solution of the surfactant, at sufficient shear and for a
sufficient period of time to form a gel phase, having at least 85%
by weight silicone polymer content, then adding catalyst if
required, then diluting the gel phase with further water to the
desired silicone polymer content of at least 75%.
32. The composition of claim 1, prepared by mixing siloxane polymer
and optionally crosslinker and optionally catalyst, with surfactant
and water, or with an aqueous solution of the surf actant, at
sufficient shear and for a sufficient period of time to form a gel
phase, having at least 85% by weight silicone polymer content, then
diluting the gel phase with further water to the desired silicone
polymer content of at least 75%.
33. The composition of claim 1, prepared by mixing siloxane polymer
and if required, catalyst, with surfactant and water at sufficient
shear and for a sufficient period of time to form a gel phase,
having at least 85% by weight silicone polymer content, then
adding, if required, crosslinker to the emulsion, then diluting the
gel phase with further water to the desired silicone polymer
content of at least 75%.
34. The composition of claim 1, prepared by mixing siloxane polymer
and crosslinker if required and catalyst if required, and any
optional formulation ingredients, with surfactant and water at
sufficient shear and for a sufficient period of time to form a gel
phase, having at least 85% by weight silicone polymer content, then
diluting the gel phase with further water to the desired silicone
polymer content of at least 75%.
35. The composition of claim 5, wherein said filler is selected
from the group consisting of colloidal silica, fumed silica,
diatomaceous earth, ground quartz, calcium carbonate, carbon black,
titanium dioxide, magnesium hydroxide, clay, aluminum oxide,
hydrated alumina, expanded vermiculite, zinc oxide, mica, talc,
iron oxide, barium sulfate, slaked lime, and mixtures thereof.
36. The composition of claim 5, wherein the filler is selected from
the group consisting of acidic stabilized colloidal silicas,
ammonium stabilized colloidal silicas, and silicas stabilized with
volatile organic amines.
37. The composition of claim 5, wherein the filler is selected from
the group consisting of natural fibers, regenerated fibers, and
synthetic fibers.
38. The composition of claim 5, wherein the filler is selected from
the group consisting of aluminum hydroxide (trihydrate),
non-flammable fibers, ceramic or glass fibers or microspheres, and
vermiculite.
39. The composition of claim 5, wherein the filler is selected from
the group consisting of carbon black, metal coated ceramic spheres
or fibers, metal coated glass spheres or fibers, uncoated or metal
coated graphite fibers or spheres.
40. The composition of claim 7, wherein the stabilizer is an
organic amine composed of carbon, hydrogen and nitrogen atoms or
carbon, hydrogen, nitrogen, and oxygen atoms, said organic amine
being soluble in the amount of water present in the emulsion.
41. The composition of claim 7, wherein the stabilizer is added in
an amount less than 5 weight parts for each 100 weight parts of
siloxane polymer.
42. The composition of claim 7, in which the stabilizer is selected
from the group consisting of diethylamine,
2-amino-2-methyl-l-propanol, and tetramethylbutylguanidine.
43. The composition of claim 7, which also contains colloidal
silica as reinforcing filler.
44. The composition of claim 1, wherein the water has been
evaporated from the silicone latex.
45. A method of making a silicone latex having a plurality of
crosslinked polysiloxane particles, comprising the steps of:
forming a mixture having
(a) 100 weight parts siloxane polymer or polymer mixture having a
viscosity of greater than 5000 mPa.s but less than 500,000 mPa.s at
25.degree. C., the siloxane polymer or polymer mixture having at
least one polymer species of the following Formula (I):
where n is 0, 1, 2 or 3 and z is an integer from 500 to 5000,
X is hydrogen, a vinyl group, a hydroxyl group, any condensable or
hydrolyzable group,
Y is a Si atom or a Si--(CH.sub.2).sub.m --SiR.sup.1.sub.2 group,
where m is 1 to 8,
R is individually selected from the group consisting of aliphatic
alkyl, aminoalkyl, polyaminoalkyl, epoxyalkyl, alkenyl, or aromatic
groups, and
R.sup.1 is individually selected from the group consisting of X,
aliphatic, alkenyl, and aromatic groups,
(b) 0.5 to 10 weight parts of a surfactant,
(c) 0.5 to 15 weight parts water,
emulsifying the mixture into a gel phase having a silicone polymer
content of at least 85% by weight;
diluting the emulsion with further water to obtain a silicon
content of at least 75% by weight,
adding up to 5 weight parts catalyst either before or after the
emulsification or before or after the dilution; and
adding up to 20 weight parts crosslinker either before or after the
emulsification, or before or after the dilution.
46. The method of claim 45, wherein the siloxane polymer or polymer
mixture includes 1 to 50 weight parts of liquid, branched
methylpolysiloxane polymers comprising (CH.sub.3).sub.3 Si.sub.0.5,
(CH.sub.3).sub.2 SiO, and CH.sub.3 SiO.sub.1.5 units and containing
from 0.1 to 8% hydroxy groups.
47. The method of claim 45, wherein the siloxane polymer or polymer
mixture includes 1 to 50 weight parts of branched methylsiloxane
polymeric resins comprising (CH.sub.3).sub.3 Si.sub.0.5,
(CH.sub.3).sub.2 SiO, CH.sub.3 SiO.sub.1.5, and SiO.sub.2 units and
containing from 0.1 to 8% hydroxyl groups.
48. The method of claim 45, wherein the siloxane polymer or polymer
mixture includes 1 to 10 weight parts of a compatible organic
solvent.
49. The method of claim 45, comprising the additional step of
adding up to 10 weight parts filler.
50. The method of claim 45, comprising the additional step of
adding up to 20 weight parts adhesion promoter.
51. The method of claim 45, comprising the additional step of
adding up to 20 weight parts stabilizer.
52. The method of claim 45, comprising the additional step of
adding up to 20 weight parts of an silsesquioxane resin
suspension.
53. The method of claim 45, comprising the additional step of
adding up to 10 weight parts of a catalyst deactivator.
54. The method of claim 45, wherein the surfactant is present in an
amount comprising 2 to 5 weight parts.
55. The method of claim 45, wherein the surf actant is present in
an amount comprising 0.5 to less than 3 weight parts.
56. The method of claim 45, wherein the water in (c) is present in
an amount comprising 6 to 15 weight parts.
57. The method of claim 45, wherein the water is in (c) present in
an amount comprising 0.5 to less than 2 weight parts.
58. The method of claim 45, wherein the silicone latex comprises
between 80 and 92% by weight silicone polymer content.
59. The method of claim 45, wherein the silicone latex comprises
between 84 and 90% by weight silicone polymer content.
60. The method of claim 45, characterized by the fact that the
viscosity of the surfactant water phase, used in emulsifying the
siloxane phase, is less than half of the viscosity of the siloxane
phase.
61. The method of claim 45, characterized by the fact that the
viscosity of the surfactant water phase, used in emulsifying the
siloxane phase, is less than 1/10 of the viscosity of the siloxane
phase.
Description
FIELD OF THE INVENTION
This invention relates to an aqueous dispersion of crosslinked
polysiloxane which does not require thickeners or other rheology
controlling additives to achieve optimum handling characteristics
at solids contents above 75% and which, upon drying, yields an
elastomer with improved durometer, tensile and elongation
properties.
BACKGROUND OF THE INVENTION
European Patent Publication 0 463 431 A2 discloses a method for
producing emulsions from high viscosity polysiloxanes, bi-modal
polysiloxane fluids, functional polysiloxanes and mixtures thereof.
The method comprises forming a thick phase emulsion by blending a
polysiloxane, at least one primary surfactant and water. To the
blend, at least one secondary surfactant is added. The mixture is
then mixed using shear for a sufficient period of time until an
average particle size of less than 350 nanometers is achieved. The
thick phase emulsion is then diluted with additional water to the
desired silicone content to form the final emulsion.
PCT publication WO 94/09058 discloses a method for preparing
oil-in-water emulsions of oils, gums or silicone resins by kneading
a mixture of (1) a silicone phase (A) with a viscosity of at least
3 Pas or a consistency of at least 20, and (2) an aqueous phase
comprising water, at least one surfactant (B) and optionally at
least one water-soluble thickening polymer (C), wherein the
relative amounts of water, (B) and optionally (C) are such that the
aqueous phase preferably has at least as much viscosity or
consistency as the silicone phase (A), said kneading being
performed for a sufficient time and with sufficient shear to give
an oil-in-water emulsion having a particle size of 0.1-5
micrometer; and optionally by diluting the medium with water.
PCT application WO 94/09059 discloses aqueous dispersions
containing: a silicone oil (A) which is cross-linkable by
condensation, optionally in the presence of a cross-linking agent
(B), into an elastomer; optionally a cross-linking agent (B), a
silane (C) and a mineral filler (D); and a catalytic amount of a
hardening compound (E). Said dispersions are characterized in that
they are produced by kneading a mixture of 1) a silicone phase (F)
with a viscosity of at least 3 Pas, containing the oil (A) and
optionally one or more of components (B), (C), (D) or (E), and 2)
an aqueous phase comprising water and at least one surfactant (G),
wherein the weight ratio water/water+surfactant(s) is such that the
viscosity of the aqueous phase is preferably at least as high as
that of the silicone phase (F); for a sufficient time and with
sufficient shear to give an oil-in-water emulsion having a particle
size of 0.1-5 micrometers; and optionally by diluting with water
until a 25-97% dry extract is obtained; followed by adding the
components) not present in the silicone phase (F).
U.S. Pat. No. 3,355,406 to Cekada teaches silicone rubber latices
reinforced by adding a silsesquioxane having the unit formula
R"SiO.sub.3/2, wherein the R" is a member selected from the group
consisting of the methyl, ethyl, vinyl, phenyl and
3,3,3-trifluoropropyl radicals, said silsesquioxane having a
particle size in the range of 10 to 1000 A. More specifically the
invention relates to a silicone latex comprising (1) a curable
essentially linear siloxane polymer having a D.P. of at least 10
and (2) a silsesquioxane having the unit formula R"Si.sub.3/2,
wherein R" is a member selected from the group consisting of the
methyl, ethyl, vinyl, phenyl and 3,3,3-trifluoropropyl radicals,
said silsesquioxane having a particle size in the range of 10 to
1000 A. The silicone latex above can also contain a catalyst and/or
a cross-linking agent.
U.S. Pat. No. 4,788,001 to Narula teaches oil-in-water emulsions
made by a process involving the mixing of the oil and water in the
presence of three nonionic surfactants having certain HLB values.
The process is particularly useful for emulsifying an oil having a
viscosity exceeding 50,000 centipoise (50 pascal-seconds). Any oil
can be emulsified by this process, including hydrocarbon oils like
mineral oil and petrolatum, and silicones, including fluids, gums
and resins. A particularly useful emulsion prepared by this process
is an emulsion of a bi-modal silicone which contains substantial
amounts of a volatile silicone and a silicone gum.
U.S. Pat. No. 5,034,455 to Stein et al. teaches curable silicone
caulk compositions using a non-ionically stabilized
silanol-terminated polydiorganosiloxane, water, a silane
cross-linker, a tin condensation catalyst, and calcium
carbonate.
U.S. Pat. No. 51037,878 to, Cerles et al. teaches aqueous
dispersions of a silicone, crosslinkable into elastomeric state
upon removal of water therefrom under ambient conditions, well
adapted for formulation into paints and for the production of
silicone elastomer seals. The composition includes (A) 100 parts by
weight of an oil-in-water emulsion containing a stabilizing amount
of at least one anionic and/or nonionic surfactant and at least one
alkoxylated diorganopolysiloxane, (B) an effective amount of an
inorganic siliceous or non-siliceous filler material, and (C) a
catalytically effective amount of a metal curing catalyst.
U.S. Pat. No. 5,045,231 to Braun et al. teaches aqueous dispersions
of organopolysiloxanes containing the following components. (A)
organopolysiloxane having groups which can undergo condensation,
(B) condensation catalyst; (C) organopolysiloxane resin; and (D)
diorganosilanolate and/or condensation products thereof formed by
splitting off water.
U.S. Pat. No. 5,145,907 to Kalinowski et al. teaches a shelf stable
aqueous silicone emulsion which yields an elastomer upon removal of
the water, produced by combining a reactive polydiorganosiloxane
present as a cationic or nonionic emulsion of dispersed particles
in water, a cross-linker, and a tin catalyst. The tin catalyst is
in the form of a divalent tin atom combined with organic radicals.
The emulsion can be reinforced with colloidal silica without
effecting the shelf life of the reinforced emulsion.
SUMMARY OF THE INVENTION
The present invention relates to a silicone latex and a method of
producing same. The silicone latex is free of rheology modifiers,
having a plurality of crosslinked polysiloxane particles, wherein
said silicone latex has at least 75% silicone content by weight,
said silicone latex comprising
(a) a crosslinked product of (i) 100 weight parts of a siloxane
polymer or polymer mixture having a viscosity of greater than 5000
mpa.s but less than 500,000 mpa.s at 25.degree. C., and (ii) up to
20 weight parts crosslinker, the siloxane polymer or polymer
mixture having at least one polymer species of the following
Formula (I):
where n is 0, 1, 2 or 3 and z is an integer from 500 to 5000,
X is hydrogen, a vinyl group, a hydroxyl group, any condensable or
hydrolyzable group,
Y is a Si atom or a Si--(CH.sub.2).sub.m --SiR.sup.1.sub.2 group,
where m is 1 to 8,
R is individually selected from the group consisting of aliphatic
alkyl, aminoalkyl, polyaminoalkyl, epoxyalkyl, alkenyl, or aromatic
groups, and
R.sup.1 is individually selected from the group consisting of X,
aliphatic alkyl, alkenyl, and aromatic groups,
(b) 0.5 to 10 weight parts surfactant,
(c) 0.5 to 25 weight parts water, and
(d) up to 5 weight parts catalyst.
The crosslinked polysiloxane dispersion comprises a siloxane
polymer, polymer mixture, or polymer/solvent mixture, capable of
crosslinking via condensation, addition or free radical reactions,
and having a viscosity of greater than 5000 mPa.s but less than
500,000 mPa.s, if required, 0.1 to 10 weight parts of a
crosslinking agent, and, if required, depending on the nature of
the catalyst and silicon cure system, 0.000001 to 10 weight parts
of a catalyst, 0.5 to 10 weight parts of a surfactant or surfactant
mixture, and 0.5 to 25 weight parts water per 100 weight parts
siloxane polymer. Optionally, adhesion promoters, pigments,
reinforcing or non-reinforcing fillers, silicone resins,
stabilizers, freeze/thaw additives, etc. may also be added to the
dispersion. The dispersion is produced by mixing at least the
silicone polymer, surfactant and 1-10 parts by weight, preferably
2-6 parts by weight of water under sufficient shear and for a
sufficient period of time to obtain a high solids "oil-in-water"
emulsion forming a characteristic clear gel phase having at least
90% polymer solids content and having particle sizes between 0.1
and 5 micrometers, preferably between 0.2 and 2 micrometers.
Cross-linker, if required, and catalyst, if required, and optional
further ingredients may be added directly to the high solids clear
gel phase or after dilution of the clear gel with water to the
desired solids content. Alternatively, either cross-linker or
catalyst, or both, as well as one or all of the further optional
ingredients may be added to the mixture prior to the emulsification
in to the gel phase. In any case, it is important for the practice
of the instant invention that a high solids gel is formed first
after the emulsification step, prior to dilution of the emulsion
with further water. The clear gel high solids emulsion containing
silicone polymer, water and surfactant and optionally cross-linker
and catalyst is shelf-stable and may be stored as an intermediate
for up to 24 months. In order to practice the instant invention it
is not required to match the viscosities of the silicone phase and
the surfactant/water phase. Viscosities of the silicone and
surfactant/water phases may differ by more than a factor of 2, and
excellent results have been obtained, when the viscosities of the
two phases differed as much as a factor of 1000. The crosslinked
polysiloxane dispersion can be transformed into an elastomer by the
removal of water.
The present invention represents several significant advances in
the art. First, the process of making the dispersion is improved
since the high solids gel phase provides for a higher shear and
lower particle size distribution. Second, the process of making the
dispersion is further improved in as far as it does not require
close matching of the viscosities of the silicone polymer phase and
the water/surfactant phase. Both processes are not known in the
art. Finally, the present invention teaches that the addition of
certain types of fillers, in particular, ammonium treated colloidal
silica, can alter the physical characteristics of the resulting
elastomer and also achieve excellent heat stability. A further
advantage of the present invention is that due to the high polymer
solids content of the diluted gel (above 75%), the composition does
not require thickeners or other rheology modifiers to achieve
excellent handling characteristics, such as desired extrusion rate
and "body" of the dispersion (resistance of the wet material felt
during tooling of the dispersion) Further, the absence of
thickener(s) makes possible the manufacture of a "clear" sealant,
since the thickener is opaque and clouds the dispersion. A further
advantage of the present invention is the versatility of the
process, allowing mixing of silicone polymer, water, surfactant,
and optionally cross-linker and catalyst in the manufacture of a
high solids oil-in-water emulsion as a gel phase intermediate. The
gel phase intermediate can be used immediately after preparation,
or stored for up to 24 months. The high solids gel is then diluted
with water to form a dispersion having greater than 75% silicone
solids content. The gel can be further processed by adding
additional ingredients and diluting the dispersion to the desired
solids content. Finally, the present invention can be practiced
with a wide variety of silicon cure chemistries which allows for
manufacture of products with improved shelf-life, compatibility,
and low toxicity.
DETAILED DESCRIPTION OF THE INVENTION
The invention comprises a) a crosslinked polysiloxane dispersion
formed from a siloxane polymer or polymer mixture, capable of
crosslinking via condensation, addition or free radical reactions,
and having a viscosity of greater than 5000 mPa.s but less than
500,000 mPa.s; b) if required, 0.1 to 10 weight parts of a
crosslinking agent; c) if required, depending on the nature of the
catalyst and silicon cure system, 0.000001 to 10 weight parts of a
catalyst; d) 0.5 to 10 weight parts of a surfactant or surfactant
mixture; and e) 0.5 to 25 weight parts water per 100 weight parts
siloxane polymer. Optionally, adhesion promoters, pigments,
reinforcing or non-reinforcing fillers, silicone resins,
stabilizers, freeze/thaw additives, etc. may also be added to the
dispersion. The dispersion is produced by mixing at least the
silicone polymer, surfactant and 1-10 parts by weight, preferably
2-6 parts by weight of water under sufficient shear and for a
sufficient period of time to obtain a high solids "oil-in-water"
emulsion forming a characteristic clear gel phase having at least
90% polymer solids content and having particle sizes between 0.1
and 5 micrometers, preferably between 0.2 and 2 micrometers.
Cross-linker, if required, and catalyst, if required, and optional
further ingredients may be added directly to the high solids clear
gel phase to crosslink the silicone polymer within the emulsion
particles forming the crosslinked polysiloxane dispersion. The
crosslinker and catalyst may be added directly to the high solids
clear gel phase or after dilution of the clear gel with water to
the desired silicone content of at least 75% by weight.
Alternatively, either cross-linker or catalyst, or both, as well as
one or all of the further optional ingredients may be added to the
mixture prior to the emulsification step. In any case, it is
important for the practice of the instant invention that a high
solids gel is formed first after the emulsification step, prior to
dilution of the emulsion with further water to achieve the silicone
content of at least 75% by weight. The crosslinked polysiloxane
dispersion can be transformed into an elastomer upon the removal of
water.
As used herein, the term "silicone content" means the total amount
by weight of silicone polymer, polymer mixture and crosslinker. The
term "rheology modifier" as used herein means a composition, such
as a thickener, added primarily for the purpose of altering the
rheological properties of the latex dispersion. Typical rheological
modifiers include, but are not limited to, polyvinyl alcohols,
polyethylene glycols, polyvinyl pyrrolidones, polyacrylates of
alkaline metals, carrageenans, alginates, carboxymethylcelluloses,
methylcelluloses, hydroxypropylcelluleoses, hydroxyethylcelluloses,
and xanthin gum.
Polymers, Polymer Mixtures, Polymer/Solvent Mixtures
The siloxane polymers or polymer mixtures used as starting
materials for the present invention are well known to those skilled
in the art. These polymers are characterized as having a viscosity
of greater than 5000 mPa.s but less than 500,000 mPa.s measured at
25.degree. C. The siloxanes include, for example, polymers
described by the following Formula (I):
where n is 0, 1, 2 or 3 and z is an integer from 500 to 5000, X is
hydrogen, a vinyl group, a hydroxyl group, any condensable or
hydrolyzable group, Y is a Si atom or a Si--(CH2).sub.m
--SiR.sup.1.sub.2 group, with m being a positive integer, R is
individually selected from the group consisting of aliphatic
aminoalkyl, polyaminoalkyl, epoxyalkyl, alkenyl organic, or
aromatic groups, and R.sup.1 is individually selected from the
group consisting of X, aliphatic and aromatic groups.
X can be hydrogen, a vinyl group, a hydroxyl group, or any
condensable or hydrolyzable group. The term "hydrolyzable group"
means any group attached to the silicon which is hydrolyzed by
water at room temperature. The hydrolyzable group X includes
hydrogen, halogen atoms such as F, Cl, Br or I; groups of the
formula --OY when Y is any hydrocarbon or halogenated hydrocarbon
group such as methyl, ethyl, isopropyl, octadecyl, allyl, hexenyl,
cyclohexyl, phenyl, benzyl, beta-phenylethyl, any hydrocarbon ether
radical such as 2-methoxyethyl, 2-ethoxyisopropyl,
2-butoxyisobutyl, p-methoxyphenyl or --(CH.sub.2 CH.sub.2 O).sub.2
CH.sub.3 ; or any N,N-amino radical such as dimethylamino,
diethylamino, ethylmethylamino, diphenylamino, or
dicyclohexylamino. X can also be any amino radical such as
NH.sub.2, dimethylamino, diethylamino, methylphenylamino or
dicyclohexylamino; any ketoxime radical of the formula
--ON.dbd.CM.sub.2 or --ON.dbd.CM' in which M is any monovalent
hydrocarbon or halogenated hydrocarbon radical such as those shown
for Y above and M' is any divalent hydrocarbon radical both
valences of which are attached to the carbon, such as hexylene,
pentylene or octylene; ureido groups of the formula
--N(M)CONM".sub.2 in which M is defined above hydrocarbon radical
such as those shown for Y above and M" is H or any of the M
radicals; carboxyl groups of the formula --OOCMM" in which M and M"
are defined above or halogenated hydrocarbon radical as illustrated
for Y above, or carboxylic amide radicals of the formula
--NMC.dbd.O(M") in which M and M" are defined above. X can also be
the sulfate group or sulfate ester groups of the formula--OSO.sub.2
(OM) where M is defined above hydrocarbon or halogenated
hydrocarbon radical illustrated for Y; the cyano group; the
isocyanate group; and the phosphate group or phosphate ester groups
of the formula --OPO(OM).sub.2 in which M is defined above.
The most preferred groups of the invention are hydroxyl groups or
alkoxy groups. Illustrative examples of the alkoxy groups are
methoxy, ethoxy, propoxy, butoxy, isobutoxy, pentoxy, hexoxy,
2-ethylhexoxy, and the like; alkoxy radicals such as
methoxymethoxy, ethoxymethoxy, and the like; and alkoxyaryloxy such
as ethoxyphenoxy and the like. The most preferred alkoxy groups are
methoxy or ethoxy.
R is individually selected from the group consisting of aliphatic,
alkyl, aminoalkyl, polyaminoalkyl, epoxyalkyl, alkenyl organic, and
aromatic aryl groups. Most preferred are the methyl, ethyl, octyl,
vinyl, allyl, and phenyl groups.
R.sup.1 is individually selected from the group consisting of X,
hydrogen, vinyl, aliphatic, alkyl, alkenyl, and aromatic groups.
Most preferred are methyl, ethyl, octyl, trifluoropropyl, vinyl,
and phenyl groups.
When the siloxane polymer of formula (I) has an average of more
than two condensable or hydrolyzable groups per molecule, it is not
necessary to have a cross-linker present in order to form a
crosslinked polymer. The condensable or hydrolyzable groups on
different siloxane molecules can react with each other to form the
required crosslinks.
The siloxane polymer of the present invention can be a single
siloxane represented by the aforesaid formula, or mixtures of
siloxanes represented by the aforesaid formula, or solvent/polymer
mixtures, and the term "polymer mixture" is meant to include any of
these types of polymers or mixtures of polymers.
The siloxane polymer of the present invention can be a mixture of
different kinds of molecules, for example long chain linear
molecules and short chain linear or branched molecules. These
molecules may react with each other to form a crosslinked network
such siloxanes which can take the place of more conventional
cross-linkers are illustrated by low molecular weight organosilicon
hydrides, such as polymethylhydrogen-siloxane, low molecular weight
copolymers containing methylhydrogensiloxy and dimethylsiloxy
groups, --(OSi(OEt).sub.2 --, (ethylpolysilicate), (OSiMeC.sub.2
H.sub.4 Si(OMe).sub.3).sub.4, and (OSi(Me)ON.dbd.CR'.sub.2).sub.4,
where Me is methyl and Et is ethyl.
The siloxane polymer of the present invention, thus, more
advantageously also comprises mixtures of siloxane polymers of
formula (I), exemplified by, but not limited to, mixtures of
a,w-hydroxysiloxy terminated siloxanes and of
a,w-bis(triorganosiloxy) terminated siloxanes, mixtures of
a,w-hydroxylsiloxy terminated siloxanes and of
a-hydroxy,w-triorgano-siloxy terminated siloxanes, mixtures of
a,w-dialkoxysiloxy terminated siloxanes and of a,w-triorganosiloxy
terminated siloxanes, mixtures of a,w-dialkoxysiloxy terminated
siloxanes and of a,w-hydroxysiloxy terminated siloxanes, mixtures
of a,w-hydroxysiloxy terminated siloxanes and of
a,w-triorganosiloxy terminated
poly(diorgano)(hydrogenorgano)siloxane co-polymers, etc. The
siloxane polymer of the invention can also comprise mixtures of
siloxane polymers of formula (I) as described above with liquid,
branched methylpolysiloxane polymers ("MDT fluids") comprising a
combination of recurring units of the formulae:
______________________________________ (CH.sub.3).sub.3 Si.sub.0.5
("M") (CH.sub.3).sub.2 SiO ("D") CH.sub.3 SiO.sub.1.5 ("T")
______________________________________
and containing from 0.1 to 8% hydroxyl groups. The fluids may be
prepared by co-hydrolysis of the corresponding chloro- or
alkoxysilanes, as described in U.S. Pat. Nos. 3,382,205; 3,661,817;
3,714,089; 4,356,116; 4,468,760; 5,175,057 and Belgian Patent No.
0,877,267. The proportion of MDT fluids added should not exceed 50
parts, preferably of 1 to 20 parts by weight, per 100 parts by
weight of the polymer of formula (I), in order to achieve improved
physical properties and adhesion of the resultant polymers. The
siloxane polymer of the present invention can also comprise
mixtures of siloxane polymers of formula (I) with liquid or solid,
branched methylsiloxane polymeric resins comprising a combination
of recurring units of the formulae:
______________________________________ (CH.sub.3).sub.3 Si.sub.0.5
("M") (CH.sub.3).sub.2 SiO ("D") CH.sub.3 SiO.sub.1.5 ("T")
SiO.sub.2 ("Q") ______________________________________
and containing from 0.1 to 8% hydroxyl groups, the fluids may be
prepared by co-hydrolysis of the corresponding chloro- or
alkoxysilanes, as described in U.S. Pat. Nos. 2,676,182; 2,441,320;
4,707,531; 5,070,175; EP 0,529,547; 0,535,687; DE 4,124,588; JP
05,098,012; WO 93/23455. The MDTQ fluid/resin may be added in a
proportion not exceeding 50 parts, preferably of 1 to 10 parts by
weight, per 100 parts by weight of the polymer of formula (I) to
improve physical properties and adhesion of the resultant polymers.
MDTQ fluids/resins can also be mixed with MDT fluids and the
polymers of Formula (I). Finally the siloxane polymer can comprise
mixtures of siloxane polymers of Formula (I) with compatible
organic solvents, to form organic polymer/solvent mixtures. These
organic solvents are exemplified by, but not limited to,
organophosphate esters, such as trioleylphosphate,
trioctylphosphate, or tetraethyleneglycolmonolaurylether-phosphate,
as disclosed in U.S. Pat. No. 4,147,855 and German Patent No.
2,802,170 (incorporated by reference); alkanes, such as hexane,
heptanes; and higher paraffins, aromatic solvents, such as toluene,
benzene; etc. The polymer solvent mixtures can also be added with
MDT fluids and/or MDTQ fluids to the polymer of Formula I. Any of
the above mixtures of polymers or polymer/solvents can be prepared
by mixing the ingredients prior to emulsification or by emulsifying
them individually and then mixing the emulsions.
Surfactants
The surfactant of the present invention is selected from nonionic
surfactants, cationic surfactants, anionic surfactants, amphoteric
surfactants and mixtures thereof. The term "surfactant" is meant to
describe a surfactant selected from these categories or a mixture
of surfactants from the above referenced categories. The surfactant
is present in the composition in an amount of 0.5 to 10 parts by
weight, preferably 2 to 10 parts by weight, based on 100 parts by
weight of siloxane polymer. Surfactant in an amount from 0.5 to 3
parts by weight based on 100 parts by weight of siloxane polymer
may also be used to achieve desirable results.
Most preferred are nonionic surfactants known in the art as being
useful in emulsification of polysiloxanes. Useful nonionic
surfactants may be exemplified, but not limited to, polyoxyalkylene
alkyl ethers, polyoxyalkylene sorbitan esters, polyoxyalkylene
esters, polyoxyalkylene alkylphenyl ethers, ethoxylated amides,
ethoxylated siloxanes, block copolymers of propylene oxide and
ethylene oxide and others. Non-ionic surfactants commercially
available and useful in the instant invention may be further
exemplified by, but not limited to, TERGITOL TMN-6, TERGITOL 15S40,
TERGITOL 15S3, TERGITOL 15S5, and TERGITOL 15S7 produced by Union
Carbide Corporation (Danbury, Conn.), BRIJ 30 and BRIJ 35 produced
by ICI CHEMICALS (Wilmington, Del.) and TRITON X405 produced by
ROHM AND HAAS (Philadelphia, Pa.) MAKON 10 produced by STEPAN
Company (Northfield, Ill.), and ETHOMID O/17 produced by AKZO Inc.
(Chicago, Ill.) and PLURONIC F38 produced by BASF Corp (Parsippany,
N.J.) and Dow Corning 5211 and 5212 (Dow Corning Corp, Midland,
Mich.),
Cationic and anionic surfactants known in the art as being useful
in emulsification of polysiloxanes are also useful as the
surfactant in the instant invention. Suitable cationic surfactants
include, but are not limited to, aliphatic fatty amines and their
derivatives such as dodecylamine acetate, octadecylamine acetate
and acetates of the amines of tallow fatty acids; homologues of
aromatic amines having fatty chains such as dodecylanalin; fatty
amides derived from aliphatic diamines such as undecylimidazoline;
fatty amides derived from disubstituted amines such as
oleylaminodiethylamine; derivatives of ethylene diamine; quaternary
ammonium compounds such as tallow trimethyl ammonium chloride,
dioctadecyldimethyl ammonium chloride, didodecyldimethyl ammonium
chloride and dihexadecyldimethyl ammonium chloride; amide
derivatives of amino alcohols such as beta-hydroxyethylsteraryl
amide; amine salts of long chain fatty acids; quaternary ammonium
bases derived from fatty amides of di-substituted diamines such as
oleylbenzylamino-ethylene diethylamine hydrochloride; quaternary
ammonium bases of the benzimidazolines such as methylheptadecyl
benzimidazole hydrobromide; basic compounds of pyridinium and its
derivatives such as cetylpyridinium chloride; sulfonium compounds
such as octadecylsulfonium methyl sulfate; quaternary ammonium
compounds of betaine such as betaine compounds of diethylamino
acetic acid and octadecylchloro-methyl ether; urethanes of ethylene
diamine such as the condensation products of stearic acid and
diethylene triamine; polyethylene diamines; and
polypropanolpolyethanol amines.
Cationic surf actants commercially available and useful in the
instant invention include, but are not limited to ARQUAD T27W,
ARQUAD 16-29, ARQUAD C-33, ARQUAD T50, ETHOQUAD T/13 ACETATE, all
manufactured by AKZO CHEMIE (Chicago, Ill.).
Suitable anionic surfactants include, but are not limited to,
sulfonic acids and their salt derivatives. The anionic surfactants
useful in the instant invention can be exemplified by, but are not
limited to, alkali metal sulforicinates; sulfonated glycerol esters
of fatty acids such as sulfonated monoglycerides of coconut oil
acids; salts of sulfonated monovalent alcohol esters such as sodium
oleylisethionate; amides of amino sulfonic acids such as the sodium
salt of oleyl methyl tauride; sulfonated products of fatty acids
nitrites such as palmitonitrile sulfonate; sulfonated aromatic
hydrocarbons such as sodium alpha-naphthalene monosulfonate;
condensation products of naphthalene sulfonic acids with
formaldehyde; sodium octahydroanthracene sulfonate; alkali metal
alkyl sulfates, ether sulfates having alkyl groups of 8 or more
carbon atoms, and alkylarylsulfonates having 1 or more alkyl groups
of 8 or more carbon atoms.
Anionic surfactants commercially available and useful in the
instant invention include, but are not limited to, POLYSTEP A4,
A7,A11, A15, A15-30K, A16, A16-22, A18, A13, A17, B1, B3, B5, B11,
B12, B19, B20, B22, B23, B24, B-25, B27, B29, C-OP3S; ALPHA-STEP
ML40, MC48; STEPANOL MG; all produced by STEPAN Company
(Northfield, Ill.), HOSTAPUR SAS produced by HOECHST CELANESE
(Chatham, N.J.). HAMPOSYL C30 and L30 produced by W.R.GRACE &
CO. (Lexington, Mass.).
Suitable amphoteric surfactants include, but are not limited to,
glycinates, betaines, sultaines and alkyl aminopropionates. These
can be exemplified by cocoamphglycinate, coco-
amphocarboxy-glycinates, cocoamidopropylbetaine, lauryl betaine,
cocoamido-propylhydroxy- sultaine, laurylsulataine, and
cocoamphodipropionate.
Amphoteric surfactants commercially available and useful in the
instant invention include, but are not limited to, REWOTERIC AM
TEG, REWOTERIC AM DLM-35, REWOTERIC AM B14 LS, REWOTERIC AM CAS,
REWOTERIC AM LP produced by SHEREX CHEMICAL CO. (Dublin, OH).
Water
In addition to adding the surfactant to the polysiloxane,
polysiloxane polymer mixture, polysiloxane/solvent mixture, or
polysiloxane/organic polymer mixture, the dispersion also includes
a predetermined amount of water. The water is present in the
composition in an amount of 0.5 to 25 parts by weight of siloxane
polymer, and is preferably present in the amount of 6 to 15 parts
by weight of siloxane polymer. Water in an amount less from 0.5 to
2 parts by weight of siloxane polymer may also be used to achieve
desirable results.
Emulsification Process
After the mixture of siloxane polymer, surfactant and water is
formed, the mixture is emulsified by mixing with sufficient shear
and for a sufficient period of time to form a high solids gel
phase. Either cross-linker or catalyst, or both, may be added to
the mixture prior to or after emulsification. The mixing will
preferably take place at a temperature on the order of 10.degree.
C. to 70.degree. C. Further formulation optional ingredients, such
as adhesion promoters, pigments, fillers, etc. may be added either
prior or after emulsification. If cross-linker, catalyst, and/or
optional ingredients are added after the emulsification step, they
may be added either prior or after diluting the gel phase with
water to the desired solids content. The gel phase will have a
polymer solids content of at least 90%, preferably in the range of
90% to 96%. The gel content may be as high 96-98% polymer.
It is anticipated that in industrial production, any type of mixing
equipment may be used to perform the emulsification step, such as
batch mixers, planetary mixers, continuous compounders such as
single or multiple screw extruders, dynamic or static mixers,
colloid mills, homogenizers, and sonolators or combinations of
these equipments, such as sonolators and static mixers, batch
mixers and dynamic mixers, or dynamic and static mixers.
High Solids Gel Intermediate
The high solids gel phase formed by emulsifying siloxane polymer,
surfactant, and water and having a polymer solids content of
greater than 90% is shelf-stable and can be stored for up to 24
months prior to further processing.
Dilution Step
After emulsification, the gel phase is diluted with water to
achieve a silicone solids content of greater than 75%. Generally,
amounts in the range of 5 to 30 parts by weight is added to achieve
a solids content in the range of 75% to 98%. A more preferred
solids range is 80-92% and the most preferred range is 84-90%. The
high silicone solids content of the final dispersion is critical
and distinguishes the present invention over the prior art. A
silicone latex having a silicone solids content of greater than 75%
allows the silicone latex to be used as a sealant without the need
for thickeners or fillers. This is in contrast to the prior art,
for example European Patent Publication 0 463 431 A2, PCT
publication WO 94/09058, and PCT application WO 94/09059, which do
not teach a method of producing a dispersion of crosslinked
silicone latex having a silicone solids content of greater than
75%, and teaches the use of a thickener. The water is added to
achieve the desired product consistency or to facilitate the
addition of other components of the composition, such as fillers,
pigments, etc.
Adhesion Promoters
Adhesion promoters may be added as optional ingredient to the
compositions taught by the present invention. They may be added
either before or after the emulsification step. If added after the
emulsification step, they may be added either before or after
diluting the high solids gel phase with water to the desired solids
content. Suitable adhesion promoters are exemplified by, but not
limited to, silanes of the formula
where n is 0, 1 or 2, and X is hydrogen, a vinyl group, a hydroxyl
group or condensable or hydrolyzable group of the same definition
as used above, and R is individually selected from the group
consisting of aliphatic alkyl, aminoalkyl, polyaminoalkyl,
epoxyalkyl, alkenyl organic, or aromatic aryl groups as defined
above.
Silanes or siloxanes particularly useful in the practice of the
present invention with addition cure systems are those that have
both SiH and SiX functionalities on the same molecule. An example
of such a silane is:
where u is a positive integer less than 5000.
Cross-linkers, Catalysts, Cure Chemistries
The cross-linkers and catalysts of the present invention depend on
the type of silicon cure system employed to cure the composition.
These curing mechanisms are well known to those skilled in the art,
and are discussed below generally. It is of course contemplated
that in accordance with the method of the present invention, the
cross-linkers or catalysts may be added either individually before
or after emulsification, or both added before or after
emulsification.
Cure Systems
One class of silicon cure systems involves condensation reactions,
for instance between silanol (Si--OH) and siliconhydride (Si--H)
groups; between silanol (Si--OH) and hydrolyzable or condensable
silyl groups, such as Si--OC(O)CH.sub.3, Si--NR.sub.2,
Si--ON.dbd.CR.sub.2, etc; between siliconhydride and hydrolyzable
or condensable groups; between two hydrolyzable or condensable
groups of the same or different species; and the like. One example
of this cure system is the reaction between a siloxane polymer
bearing silanol groups and a cross-linking compound bearing
hydrolyzable groups directly attached to silicon atom(s) Another
example of this cure system is the reaction between a siloxane
polymer bearing hydrolyzable or condensable groups directly
attached to silicon atom(s) and a cross-linking compound bearing
silanol groups. Another example of this cure system is the reaction
between two siloxane polymers bearing hydrolyzable or condensable
groups attached directly to silicon atom(s) A further example of
this cure system is the reaction between a siloxane polymer bearing
hydrolyzable or condensable groups directly attached to silicon
atom(s) and a siloxane polymer bearing active hydrogen atoms, such
as in hydroxyl, ureido, mercapto, or amino groups. The following
condensation cure chemistries are considered useful for the
practice of this invention:
(a) the polymer bears hydroxyl groups attached directly to silicon
atom(s); and the cross-linking compound is a silane, a siloxane
oligomer or polymer, a siloxane resin, or a silicon modified
organic oligomer, polymer, or resin bearing hydrolyzable or
condensable groups attached directly to silicon atom(s);
(b) the polymer bears hydrolyzable or condensable groups directly
attached to silicon atom(s); and the cross-linking compound is a
siloxane oligomer or polymer, a siloxane resin, a silica, a
silicate, a siliconate, or a silicon modified organic oligomer,
polymer or resin bearing silanol groups;
(c) the polymer bears hydrolyzable or condensable groups directly
attached to silicon atom(s); and the cross-linking compound is a
silane, a siloxane oligomer or polymer, a siloxane resin, or a
silicon modified organic oligomer, polymer, or resin bearing
hydrolyzable or condensable groups attached directly to silicon
atom(s); the hydrolyzable groups on the siloxane polymer and the
cross-linking compound being the same or different; and, if the
cross-linking compound is a polymer, the first polymer and the
cross-linking compound (second polymer) being the same or different
polymers;
(d) the polymer bears hydroxyl groups attached directly to silicon
atom(s); and the cross-linking compound is a silane, a siloxane
oligomer or polymer, a siloxane resin, or a silicon modified
organic oligomer, polymer or resin bearing silicon hydride groups
and, optionally, other hydrolyzable or condensable groups attached
directly to silicon atom(s);
(e) the polymer bears hydrolyzable or condensable groups attached
directly to silicon atom(s); and the cross-linking compound is a
silane, a siloxane oligomer or polymer, a siloxane resin, or a
silicon modified organic oligomer, polymer or resin bearing silicon
hydride groups and, optionally, other hydrolyzable or condensable
groups attached directly to silicon atom(s);
(f) the polymer bears silicon hydride groups and, optionally, other
hydrolyzable or condensable groups attached directly to silicon
atom(s) and the crosslinking compound is a silane, a siloxane
oligomer or polymer, a siloxane resin, or a silicon modified
organic oligomer, polymer, or resin bearing hydrolyzable or
condensable groups;
(g) the polymer bears silicon hydride groups and, optionally, other
hydrolyzable or condensable groups attached directly to silicon
atom(s); and the crosslinking compound is a siloxane oligomer or
polymer, a siloxane resin, a silica, a silicate, a siliconate, or a
silicon modified organic oligomer, polymer, or resin bearing
silanol groups;
The number of reactive radicals on the siloxane polymer and the
cross-linker determine, whether a cured elastomer is obtained. An
elastomeric network is being formed by the condensation cure, if
the sum of the reactive radicals on the polymer and the reactive
radicals on the cross-linker is at least 5. For example, if the
polymer has two hydroxysiloxy groups and the cross-linker has three
condensable groups directly attached to silicon atom(s), an
elastomer is obtained. An elastomer is also obtained by reacting a
siloxane polymer bearing a total of four hydrolyzable groups
attached to two silicon atoms with another siloxane polymer bearing
two silanol groups. However, no elastomer is obtained by reacting a
siloxane polymer bearing two silanol groups with a cross-linker
bearing two hydrolyzable groups directly attached to silicon
atom(s).
Some condensation cure chemistries require a catalyst to effect the
reaction between polymer and crosslinking compound. Suitable
silanol condensation catalysts are well know in the art. Examples
of suitable condensation catalysts preferably employed in the
condensation reactions (a) to (g) are: (organo)metallic compounds,
amino compounds, carboxylic acids, salts of amino compounds with
carboxylic acids or other acids, low molecular weight polyamide
resins obtained by the reaction of excess polyamines with polybasic
acids, the reaction products between epoxy compounds and an excess
of polyamines, or mixtures of above condensation catalysts.
Specific examples of (organo)metallic compounds are the salts of a
carboxylic acids, alcoholates and halides of the metals lead, zinc,
zirconium, titanium, antimony, iron, cadmium, tin, barium, calcium
or manganese as taught in U.S. Pat. Nos. 3,355,406, 3,706,695,
4,100,124, 4,288,356, 4,587,288, and 4,608,412, which are
incorporated herein by reference. Further specific examples of
(organo)metallic compounds are titanic acid esters and chelates,
such as tetrabutyl titanate, tetrapropyl titanate, titanium
tetraacetyl acetonate, or dibutoxytitanium bis(ethyl acetoacetate);
zirconium chelates, such as zirconium tetraacetyl acetonate; organo
aluminum compounds, such as aluminum trisacetyl acetonate, aluminum
trisethyl acetoacetonate, or diisopropoxy aluminum ethyl
acetoacetonate, etc. Specific examples of amino compounds are butyl
amine, octyl amine, dibutyl amine, monoethanol amine, diethanol
amine, triethanol amine, diethylene triamine, triethylene
tetramine, triethylene diamine, oleyl amine, cyclohexyl amine,
benzyl amine, diethylaminopropyl amine, xylylene diamine,
guanidine, diphenyl guanidine, 2,4,6-tris (dimethyl aminomethyl)
phenol, morpholine, N-methyl morpholine, 2-ethyl-4-methylimidazole,
1,8-diazabicyclo (5,4,0) undecene-7, aminosilanes, such as g-amino
propyltrimethoxysilane or
N-(b-aminoethyl)-g-aminopropylmethyldimethoxysilane. Specific
examples of carboxylic acids are formic acid, acetic acid, etc.
Particularly preferred (organo)metallic catalysts which act as
condensation catalysts are (organo)tin compounds of carboxylic
acids having from 1 to 18 carbon atom(s) and (organo)tin halides,
in particular organotin octoates, naphthenates, hexoates, laurates,
acetates, bromides and chlorides. Specific examples of such
(organo)tin compounds are tin(II)octoate, dibutyltin dilaurate,
octyltin triacetate, dioctyltin dioctoate, dioctyltin diacetate,
didecyltin diacetate, dibutyltin diacetate, dibutyltin dibromide,
dioctyltin dilaurate, and trioctyltin acetate. Preferred compounds
are tin(II)octoate and diorganotin dicarboxylates, in particular
dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin diacetate
and dioctyltin diacetate. The catalyst may also be the product of a
reaction of a tin salt, in particular of a tin dicarboxylate, with
an alkoxysilane or ethyl polysilicate, as described in U.S. Pat.
Nos. 3,862,919, 4,102,860, 4,137,249, 4,152,343. However, other tin
catalysts can also be utilized, such as a member selected from the
class consisting of stannoxanes, hydroxystannoxanes, and
monoalkoxyacylstannanes. More particularly, diacylstannoxane,
acylhydroxystannoxane, monomethoxyacylstannanes, dihalostannoxane
or halohydroxystannoxane have been found effective. If silica is
used as a reinforcing filler in the composition, divalent tin
compounds are the most preferred condensation catalysts as
described in U.S. Pat. No. 4,954,565. The divalent, stannous form
of (organo)tin compounds do not cause a reaction between the
silanol functional polymer and silica as is caused when the
tetravalent, stannic form of (organo)tin compounds are used as
catalysts. The preferred stannous catalyst is stannous octoate
(stannous bis(2-ethyl-hexanoate).
Use of co-catalysts, for example, amino compounds or carboxylic
acids, such as acetic acid, with tetravalent tin compounds, for
example, dibutyltin diacetate, allows for a significant reduction
of the (organo)tin catalyst level. When said condensation catalysts
are used, they are added in an amount preferably of from 0.01 to 20
weight parts, more preferably from 0.1 to 10 weight parts, per 100
weight parts of the silicon modified organic polymer.
Amine functional silanes added to the composition as adhesion
promoters may also catalyze condensation reactions between silanes
bearing hydrogen or hydrolyzable groups and hydroxysiloxy
endblocked siloxane polymers.
Further compounds suitable for catalyzing condensation reactions
(d) to (g) are group VIII transition metal (noble metal) compounds.
The noble metal catalyst is selected from any of those well known
to the art, such as those described in U.S. Pat. No. 3,923,705,
said patent being hereby incorporated by reference to show platinum
catalysts. A preferred platinum compound catalyst is a composition
consisting essentially of the reaction product of chloroplatinic
acid and an organosilicon compound containing terminal aliphatic
unsaturation, such as described in U.S. Pat. No. 3,419,593, said
patent being incorporated by reference. When said noble metal
catalysts are used, they are added in an amount preferably of from
0.00001 to 0.5 weight parts, more preferably from 0.00001 to 0.002
weight parts, per 100 weight parts of the silicon modified organic
polymer.
For example, in one condensation cure system useful in the present
invention, the siloxane polymer has functional groups such as
hydroxyl, condensable, or hydrolyzable group(s) attached to silicon
atom(s), and the cross-linker has silicon-hydrogen bond(s). The
polymer and the cross-linker are reacted in the presence of a
condensation catalyst, as disclosed and described in U.S. Pat. Nos.
4,310,678, 4,782,112, 4,962,153, and 4,978,710 which are
incorporated herein by reference. The silicon hydride cross-linker
can be chosen from hydrolyzable silicon hydride, polymeric or
oligomeric compounds, containing hydrogen and optionally
hydrolyzable or condensable groups bound directly to silicon
atom(s), such as polyorganohydrogensiloxane,
alkylhydrogen-cyclosiloxane, and liquid copolymers comprising
SiO.sub.2 and/or SiO.sub.3/2 units and bearing silicon-bonded
hydrogen radicals such as taught in U.S. Pat. No. 4,310,678, or
organic polymers or resins containing Si--H groups and optionally
other hydrolyzable or condensable silyl groups directly bound to
carbon atom(s) via Si--C bonds. The cross-linker may also be a
silsesquioxane containing hydrogen and optionally also alkoxy
groups bound directly to silicon atoms, as described, for example,
in U.S. Pat. No. 5,047,492, incorporated herein by reference. The
hydrolyzable silicon hydride should have at least one, but not more
than three hydrogen atoms bonded to silicon per molecule. It may
have one or two hydrolyzable atoms or groups, such as alkoxy,
bonded to silicon per molecule, such as methyldiethoxysilane.
Examples of cross-linkers are trimethylsilyl endblocked
polymethylhydrogensiloxane and methylhydrogencyclosiloxane. The SiH
functional cross-linker is added in sufficient amount to provide at
least one hydrogen atom for each hydroxyl or alkoxy group in the
polydiorganosiloxane polymer. Preferably, an excess of SiH
functional cross-linker is provided so that all hydroxyl or alkoxy
groups can be reacted. In a typical preparation, a noble metal
catalyst would be present in the composition in an amount of from
0.00001 to 0.5 parts, preferably from 0.00001 to 0.02, and more
preferably from 0.00001 to 0.002 parts by weight, any other
condensation catalyst would be present in the composition in an
amount of from 0.01 to 10 parts by weight and preferably 0.05 to 5
parts by weight per 100 weight parts of siloxane polymer, the SiH
functional cross-linker would be present in an amount of from 0.1
to 10 parts by weight per 100 parts by weight of siloxane polymer
bearing hydroxyl or hydrolyzable or condensable groups.
As an alternative to the first condensation cure system, siloxane
polymer having at least two silicon-hydrogen bonds can be reacted
in the presence of a condensation catalyst with a cross-linker
having, on average, at least two (2.0) hydroxyl or at least two
(2.0) condensable or hydrolyzable groups per molecule attached
directly to silicon atoms(s). In a typical preparation, the
catalyst would be present in the composition in the same amount as
described above, and cross-linker, depending on the type of
cross-linker utilized, in an amount of from 0.1 to 50 parts by
weight per 100 weight parts of silicon-hydrogen terminated siloxane
polymer.
In a second useful condensation cure system, the siloxane polymer
has at least two hydroxysiloxy groups, and the cross-linker has, on
average, at least two (2.0) hydrolyzable OR' groups, where R' is a
monovalent unsubstituted or substituted hydrocarbon radical bonded
to silicon atom(s) per molecule. The siloxane polymer and
cross-linker are reacted in the presence of a condensation
catalyst. The cross-linker is a silane of the formula R.sub.x
SiY.sub.4-x where x is either 0 or 1, R can be hydrogen, a
monovalent hydrocarbon radical or substituted hydrocarbon radical
having less than 7 carbon atoms, such as an alkyl or alkenyl
radical, a halogenated hydrocarbon, an aryl radical, a
functionalized hydrocarbon radical. As used here and throughout, Y
is OR', where R' can be a monovalent unsubstituted or substituted
hydrocarbon radical. Suitable silanes include ethylorthosilicate,
normal propylorthosilicate, mercaptopropyltrimethoxysilane,
methyltrimethoxysilane, phenyltrimethoxysilane,
chloropropyltrimethoxysilane, amyltriethoxysilane,
g-glycidoxy-propyltrimethoxysilane,
trifluoropropyltrimethoxysilane, ethyltrimethoxysilane,
triethoxysilane, and vinyltrimethoxysilane. The cross-linker can
also be a silsesquioxane containing alkoxy, aryloxy, alkoxyalkoxy,
or alkoxyaryloxy groups bound directly to silicon atoms, as
described, for example, in U.S. Pat. No. 5,047,492, incorporated
herein by reference. The cross-linker may also be a linear or
cyclic siloxane oligomer containing OR' groups, or an organic
polymer or resin bearing Si-OR' groups and, optionally, an
additional crosslinker having at least one hydrolyzable group per
molecule other than OR, bound directly to silicon atom(s). The
cross-linker may also be the partial hydrolysis and condensation
product (dimer, trimer, tetramer, etc.) of above cross-linkers. In
a typical preparation, the condensation catalyst would be present
in the composition in an amount of from 0.01 to 10 parts,
preferably in an amount of from 0.05 to 5 parts, and cross-linker
would be present in an amount of from 0.1 to 50 parts, preferably
in an amount from 1 to 10 parts, each by weight, based on 100 parts
by weight of siloxane polymer.
As an alternative to the second condensation cure system, the
siloxane polymer has at least two hydrolyzable OR' groups and,
optionally, other hydrolyzable or condensable group(s) other than
OR, bound to silicon atom(s). The polymer is then reacted in the
presence of a condensation catalyst as described above with a
cross-linker having, on average, at least two (2.0) hydroxyl groups
per molecule bound to silicon atom(s), In a typical preparation,
the catalyst would be present in the composition in an amount from
0.01 to 10 parts, preferably in an amount from 0.01 to 5 parts, and
the cross-linker, depending on its nature, would be present in an
amount of from 0.1 to 50 parts, preferably in an amount from 1 to
10 parts, each by weight, based on 100 parts by weight of siloxane
polymer.
As a further alternative to the second condensation cure system,
the siloxane polymer having at least two hydrolyzable OR' groups
and, optionally, other hydrolyzable or condensable group(s) other
than OR' bound to silicon atoms per molecule which can be
crosslinked in the presence of a condensation catalyst as described
above. In case the siloxane polymer has only two hydrolyzable OR'
groups and no further hydrolyzable group(s), the presence of a
cross-linker, which, on average, has at least (2.0) hydrolyzable
groups per molecule bound to silicon atom(s), is required. In case
the siloxane polymer has more than two hydrolyzable OR, groups or
two OR' groups and further hydrolyzable group(s) other than OR'
attached to silicon atoms, the presence of a cross-linker is not
required. In a typical preparation, the catalyst would be present
in the composition in an amount from 0.01 to 10 parts, preferably
in an amount from 0.01 to 5 parts, and the additional cross-linker,
if required, would be present in an amount of from 0.1 to 20 parts,
preferably in an amount from 0.1 to 10 parts, each by weight, based
on 100 parts by weight of siloxane polymer.
In a third condensation cure system useful to the practice of the
present invention, the siloxane polymer having at least two
hydroxysiloxy groups and the cross-linker having, on average, at
least two (2.0) hydrolyzable acyloxy groups per molecule bonded to
silicon atom(s), are reacted, optionally in the presence of a
condensation catalyst, as taught in U.S. Pat. No. 5,321,075, which
is incorporated herein by reference. The cross-linker can be an
acyloxy silane of the formula R.sub.x Si(O(O)CR').sub.4-x, where x
is either 0 or 1, R can be hydrogen, a monovalent hydrocarbon
radical or substituted hydrocarbon radical having less than 7
carbon atoms, such as an alkyl or alkenyl radical, a halogenated
hydrocarbon, an aryl radical, a functionalized hydrocarbon radical,
and R' can be hydrogen, a monovalent hydrocarbon or a monovalent
substituted hydrocarbon radical Examples of suitable acyloxysilane
cross-linkers include methyltriacetoxysilane,
ethyltriacetoxysilane, phenyltriacetoxysilane,
ethyltriacetoxysilane, phenyltriacetoxysilane, and
methyl-tris(benzoyloxy) silane. A preferred acyloxysilane is
vinyltriacetoxysilane. The acyloxysilane may also be pre-reacted
with a siloxane, such as (CH.sub.3).sub.3 SiO(CH.sub.3 HSiO).sub.x
((CH.sub.3 COO).sub.3 SiCH.sub.2 CH.sub.2 SiCH.sub.3 O)y
Si(CH.sub.3).sub.3, as disclosed in German Patent No. 2,316,184,
incorporated herein by reference. The cross-linker may also be a
linear or cyclic siloxane oligomer containing acyloxysiloxy groups.
The cross-linker may also be a silsesquioxane containing acyloxy
groups bound directly to silicon atom(s), an organic polymer or
resin bearing acyloxysilyl groups and, optionally, an additional
crosslinker having at least one other hydrolyzable or condensable
group per molecule other than acyloxy bound directly to silicon
atom(s). Cross-linker may also be a partial hydrolysis and
condensation product (dimer, trimer, tetramer, etc.) of above
cross-linkers. In a typical preparation, the optional catalyst
would be present in the composition in an amount of from 0 to 10
parts, preferably in an amount of from 0 to 5 parts, and the
cross-linker would be present in an amount of from 0.1 to 50 parts,
preferably in an amount from 1 to 10 parts, each by weight, based
on 100 parts by weight of siloxane polymer.
In an alternative to the third condensation cure system, the
siloxane polymer having at least two hydrolyzable acyloxy groups
and, optionally, other hydrolyzable or condensable group(s) other
than acyloxy bound to silicon atom(s), is reacted with a
cross-linker having, on average, at least two (2.0) hydroxyl groups
bound to silicon atoms, optionally in the presence of a
condensation catalyst. In a typical preparation, the optional
catalyst would be present in the composition in an amount from 0 to
10 parts, preferably in an amount from 0 to 5 parts, and the
cross-linker, depending on its nature, would be present in an
amount of from 0.1 to 50 parts, preferably in an amount from 1 to
10 parts, each by weight, based on 100 parts by weight of siloxane
polymer.
As a further alternative to the third condensation cure system,
siloxane polymer having at least two hydrolyzable acyloxy groups
and, optionally, other hydrolyzable or condensable group(s) other
than acyloxy bound to silicon atom(s), which can be crosslinked,
optionally, in the presence of a condensation catalyst as described
above. In case the siloxane polymer has only two hydrolyzable
acyloxy groups and no further hydrolyzable group(s), the presence
of a cross-linker, which, on average, has at least two (2.0)
hydrolyzable groups per molecule bonded to silicon atom(s), is
required. In case the siloxane polymer has more than two
hydrolyzable acyloxy groups or two acyloxy groups and further
hydrolyzable group(s) other than acyloxy attached to silicon atoms,
the presence of a cross-linker is not required. In a typical
preparation, the optional catalyst would be present in the
composition in an amount from 0 to 10 parts, preferably in an
amount from 0 to 5 parts, and the additional cross-linker, if
required, would be present in an amount of from 0.1 to 20 parts,
preferably in an amount from 0.1 to 10 parts, each by weight, based
on 100 parts by weight of siloxane polymer.
In a fourth condensation cure system useful to the practice of the
present invention, the siloxane polymer, having at least two
hydroxysiloxy groups, is reacted with a cross-linker, bearing, on
average, at least two (2.0) hydrolyzable oximo groups per molecule
bonded to silicon atom(s), optionally in the presence of a
condensation catalyst. The system is described in detail in U.S.
Pat. Nos. 4,618,642 and 4,954,565 which are incorporated herein by
reference. The cross-linker can be an oximosilane of formula
RxSi(O--N.dbd.C(R'R")).sub.4-x, where x is either 0 or 1, and R can
be hydrogen, a monovalent hydrocarbon radical or substituted
hydrocarbon radical having less than 7 carbon atoms, such as an
alkyl or alkenyl radical, a halogenated hydrocarbon, an aryl
radical, a functionalized hydrocarbon radical, and R' and R" are
individually selected from the group consisting of hydrogen,
monovalent hydrocarbon or monovalent substituted hydrocarbon
radical Examples of suitable acyloxy-silane cross-linkers include
methyltris(methylethylketoximo)-silane,
methyltris(dimethylketoximo)silane,
methyltris(diethylketoximo)silane,
vinyltris(methylethylketoximo)silane,
vinyltris(methylisobutylketoximo) silane,
tetra(methylisobutylketoximo)silane. The cross-linker may also be
an oximosilane of the formula R.sup.4.sub.a (R.sup.3 SiO).sub.b
Si(ONCR.sup.1 R.sup.2).sub.4-(a+b) with R.sup.1, R.sup.2 R.sup.3
and R.sup.4 independently selected from the group consisting of 1-8
carbon alkyl or fluoroalkyl, 5-6 carbon cycloalk(en)yl, 2-8 carbon
alkenyl or aryl, and a is either 0 or 1, and b is either 1 or 2, as
disclosed in German Patent No. 3,903,337, incorporated herein by
reference. The cross-linker may also be a linear or cyclic siloxane
oligomer containing oximosiloxy groups, a silsesquioxane containing
oximo and, optionally, other hydrolyzable or condensable groups
bound directly to silicon atoms, an organic polymer or resin
bearing oximosilyl groups and, optionally, an additional
crosslinker having on average at least one other hydrolyzable or
condensable group per molecule other than oximo bound directly to
silicon atoms. The cross-linker may also be a partial hydrolysis
and condensation product (dimer, trimer, tetramer, etc) of above
cross-linkers. In a typical preparation, the optional condensation
catalyst, depending on its nature, would be present in the
composition in an amount of from 0 to 10 parts, preferably in an
amount of from 0 to 5 parts, and the cross-linker would be present
in an amount of from 0.1 to 50 parts, preferably in an amount from
1 to 10 parts, each by weight, based on 100 parts by weight of
siloxane polymer.
In an alternative to the fourth condensation cure system, the
siloxane polymer having at least two hydrolyzable oximo groups and,
optionally, other hydrolyzable or condensable group(s) other than
oximo bound to silicon atom(s), is reacted with a cross-linker
having, on average, at least two (2.0) hydroxyl groups per molecule
bound to silicon atoms, optionally in the presence of a
condensation catalyst. In a typical preparation, the optional
catalyst would be present in the composition in an amount from 0 to
10 parts, preferably in an amount from 0 to 5 parts, and the
cross-linker, depending on its nature, would be present in an
amount of from 0.1 to 50 parts, preferably in an amount from 1 to
10 parts, each by weight, based on 100 parts by weight of siloxane
polymer.
As a further alternative to the fourth condensation cure system,
siloxane polymer having at least two hydrolyzable oximo groups and,
optionally, other hydrolyzable or condensable group(s) other than
oximo bound to silicon atom(s), which can be crosslinked,
optionally, in the presence of a condensation catalyst as described
above. In case the siloxane polymer has only two hydrolyzable oximo
groups and no further hydrolyzable group(s), the presence of a
cross-linker, which, on average, has at least two (2.0)
hydrolyzable groups per molecule bonded to silicon atom(s), is
required. In case the siloxane polymer has more than two
hydrolyzable oximo groups or two oximo groups and further
hydrolyzable group(s) other than oximo attached to silicon atoms,
the presence of a cross-linker is not required. In a typical
preparation, the optional catalyst would be present in the
composition in an amount from 0 to 10 parts, preferably in an
amount from 0 to 5 parts, and the additional cross-linker, if
required, would be present in an amount of from 0.1 to 20 parts,
preferably in an amount from 0.1 to 10 parts, each by weight, based
on 100 parts by weight of siloxane polymer.
In a fifth condensation cure system useful to the practice of the
present invention, the siloxane polymer, having at least two
hydroxysiloxy groups, is reacted with a cross-linker, having, on
average, at least two (2.0) hydrolyzable amino groups per molecule
bonded directly to silicon atom(s), optionally in presence of a
condensation catalyst. The cross-linker can be a silazane of
formula (R.sub.n Si(NR'.sub.2).sub.4-n), as described in U.S. Pat.
Nos. 3,032,528, 3,338,868, 3,464,951, and 3,408,325, incorporated
herein by reference, where R is hydrogen, monovalent hydrocarbon
radical or substituted hydrocarbon radical having less than 7
carbon atoms, functionalized hydrocarbon radicals, nitrogen
compounds of the formula --N.dbd.CR'.sub.2 or --NR'COR' or
--NR'.sub.2 or --NR", where R' is either hydrogen, monovalent
hydrocarbon or monovalent substituted hydrocarbon radical, and R"
is cycloalkyl radical, and n is either 0 or 1 A preferred
cross-linker is methyltris(cyclohexylamine)silane. The cross-linker
may also be a linear or cyclic siloxane oligomer containing
aminosiloxy groups, a silsesquioxane containing amino and,
optionally, other hydrolyzable or condensable groups bound directly
to silicon atom(s), an organic polymer or resin bearing aminosiloxy
groups and, optionally, an additional crosslinker having on average
at least one other hydrolyzable or condensable group per molecule
other than oximo bound directly to silicon atom(s). The
cross-linker may also be a partial hydrolysis and condensation
product (dimer, trimer, tetramer, etc.) of above cross-linkers. In
a typical preparation, the optional condensation catalyst would be
present in the composition in an amount of from 0 to 10 parts,
preferably from 0 to 5 parts, and cross-linker in an amount of from
0.1 to 50 parts, preferably from 1 to 10 parts, each by weight,
based on 100 weight parts of siloxane polymer.
In an alternative to the fifth condensation cure system, the
siloxane polymer having at least two hydrolyzable amino groups and,
optionally, other hydrolyzable or condensable group(s) other than
amino bound to silicon atom(s), is reacted with a cross-linker
having, on average, at least two (2.0) hydroxyl groups per molecule
bound to silicon atoms, optionally in the presence of a
condensation catalyst. In a typical preparation, the optional
catalyst would be present in the composition in an amount from 0 to
10 parts, preferably in an amount from 0 to 5 parts, and the
cross-linker, depending on its nature, would be present in an
amount of from 0.1 to 50 parts, preferably in an amount from 1 to
10 parts, each by weight, based on 100 parts by weight of siloxane
polymer.
As a further alternative to the fifth condensation cure system,
siloxane polymer having at least two hydrolyzable amino groups and,
optionally, other hydrolyzable or condensable group(s) other than
amino bound to silicon atom(s), which can be crosslinked,
optionally, in the presence of a condensation catalyst as described
above. In case the siloxane polymer has only two hydrolyzable amino
groups and no further hydrolyzable group(s), the presence of a
cross-linker, which, on average, has at least two (2.0)
hydrolyzable groups per molecule bonded to silicon atom(s), is
required. In case the siloxane polymer has more than two
hydrolyzable amino groups or two amino groups and further
hydrolyzable group(s) other than amino attached to silicon atoms,
the presence of a cross-linker is not required. In a typical
preparation, the optional catalyst would be present in the
composition in an amount from 0 to 10 parts, preferably in an
amount from 0 to 5 parts, and the additional cross-linker, if
required, would be present in an amount of from 0.1 to 20 parts,
preferably in an amount from 0.1 to 10 parts, each by weight, based
on 100 parts by weight of siloxane polymer.
In a sixth condensation cure system useful to the practice of the
present invention, the siloxane polymer, having at least two
hydroxysiloxy groups, is reacted with a cross-linker, having, on
average, at least two (2.0) hydrolyzable aminoxy groups per
molecule bonded to silicon atom(s), optionally in presence of a
condensation catalyst. The cross-linker can be an aminoxysilane of
the formula R.sub.n Si(ONR'R").sub.4-n, a linear aminoxysiloxane of
the formula (R.sub.3 SiO(SiR.sub.2 O).sub.a (SiRXO).sub.b
SiR.sub.3), a cyclic aminoxysiloxane (mixture of cyclic siloxanes
containing (R.sub.2 SiO) and (RXSiO) units), as described in U.S.
Pat. Nos. 3,441,583, 3,484,471, 3,528,941, 3,817,909, 3,839,386,
4,075,154, and Japanese Patent No. 7 6,019,728, and German Patent
No. 2,640,328, incorporated herein by reference, where X is ONR'R",
R is individually selected from the group consisting of hydrogen,
monovalent hydrocarbon radical or substituted hydrocarbon radical
having less than 7 carbon atoms, functionalized hydrocarbon
radicals, nitrogen compounds of the formula --N.dbd.CR'.sub.2 or
--NR'COR' or --NR'.sub.2 or --NR", where R' and R" are either
hydrogen, a monovalent hydrocarbon or a monovalent substituted
hydrocarbon radical, and R"' is a cycloalkyl radical, and n is
either 0 or 1, and a is 0 or a positive integer, and b is an
integer greater than 2. The cross-linker can also be a
silsesquioxane containing aminoxy and, optionally, other
hydrolyzable or condensable groups bound directly to silicon atoms,
an organic polymer or resin bearing aminoxysilyl groups and,
optionally, an additional crosslinker having an average at least
one other hydrolyzable or condensable group per molecule other than
aminoxy bound directly to silicon atom(s) The cross-linker can also
be a partial hydrolysis and condensation product (dimer, trimer,
tetramer, etc.) of above cross-linkers. In a typical preparation,
the optional condensation catalyst would be present in the
composition in an amount of from 0 to 10 parts, preferably from 0
to 5 parts, and cross-linker in an amount of from 0.1 to 50 parts,
preferably from 1 to 10 parts, each by weight, based on 100 weight
parts of siloxane polymer.
In an alternative to the sixth condensation cure system, the
siloxane polymer having at least two hydrolyzable aminoxy groups
and, optionally, other hydrolyzable or condensable group(s) other
than aminoxy bound to silicon atom(s), is reacted with a
cross-linker having, on average, at least two (2.0) hydroxyl groups
per molecule bound to silicon atoms, optionally in the presence of
a condensation catalyst. In a typical preparation, the optional
catalyst would be present in the composition in an amount from 0 to
10 parts, preferably in an amount from 0 to 5 parts, and the
cross-linker, depending on its nature, would be present in an
amount of from 0.1 to 50 parts, preferably in an amount from 1 to
10 parts, each by weight, based on 100 parts by weight of siloxane
polymer.
As a further alternative to the sixth condensation cure system,
siloxane polymer having at least two hydrolyzable aminoxy groups
and, optionally, other hydrolyzable or condensable group(s) other
than aminoxy bound to silicon atom(s), which can be crosslinked,
optionally, in the presence of a condensation catalyst as described
above. In case the siloxane polymer has only two hydrolyzable
aminoxy groups and no further hydrolyzable group(s), the presence
of a cross-linker, which, on average, has at least two (2.0)
hydrolyzable groups per molecule bonded to silicon atom(s), is
required. In case the siloxane polymer has more than two
hydrolyzable aminoxy groups or two aminoxy groups and further
hydrolyzable group(s) other than aminoxy attached to silicon atoms,
the presence of a cross-linker is not required. In a typical
preparation, the optional catalyst would be present in the
composition in an amount from 0 to 10 parts, preferably in an
amount from 0 to 5 parts, and the additional cross-linker, if
required, would be present in an amount of from 0.1 to 20 parts,
preferably in an amount from 0.1 to 10 parts, each by weight, based
on 100 parts by weight of siloxane polymer.
In a seventh condensation cure system useful to the practice of the
present invention, the siloxane polymer, having at least two
hydroxysiloxy groups, is reacted with a cross-linker, having, on
average, at least two (2.0) hydrolyzable amido groups per molecule
bonded to silicon atom(s), optionally in the presence of a
condensation catalyst. The cross-linker can be an amidosilane of
formula (R.sub.n Si(OR.sup.1).sub.m (NR.sup.2
--(CO)--R.sup.3).sub.4-(n+m)), where R is selected from the group
consisting of hydrogen, monovalent hydrocarbon radical or
substituted hydrocarbon radical having less than 7 carbon atoms,
functionalized hydrocarbon radicals, nitrogen compounds of the
formula --N.dbd.CR.sup.2.sub.2 or --NR.sup.2 COR.sup.2 or
--NR.sup.2 or --NR.sup.4, and R.sup.1 is a monovalent hydrocarbon
radical, a monovalent substituted hydrocarbon radical having less
than 7 carbon atoms, or a functionalized hydrocarbon radical having
less than 7 carbon atoms, R.sup.2 is hydrogen, or monovalent
hydrocarbon or substituted hydrocarbon radicals having less than 7
carbon atoms, and R3 is monovalent aliphatic or aromatic
hydrocarbon radical or substituted hydrocarbon radical having less
than 7 carbon atoms, or functionalized hydrocarbon radical, and
R.sup.4 is a cycloalkyl radical, and n is either 0 or 1, and m
either 0, 1 or 2, as described, for example, in U.S. Pat. Nos.
3,378,520, 4,985,476, optionally in the presence of a condensation
catalyst. Examples of preferred cross-linkers
aremethyltris(acetamido)-silane
andmethylethoxybis-(N-methylbenzamido)silane. The cross-linker may
also be a linear or cyclic siloxane oligomer containing amidosiloxy
groups. The cross-linker may also be a silsesquioxane containing
amido and, optionally, an additional crosslinker having on average
at least one other hydrolyzable or condensable groups per molecule
other than amido bound directly to silicon atoms, an organic
polymer or resin bearing amidosilyl groups and, optionally, other
hydrolyzable or condensable groups bound directly to silicon
atom(s). The cross-linker may also be a partial hydrolysis and
condensation product (dimer, trimer, tetramer, etc.) of above
cross-linkers. In a typical preparation, the optional condensation
catalyst would be present in the composition in an amount of from 0
to 10 parts, preferably from 0 to 5 parts, and cross-linker in an
amount of from 0.1 to 50 parts, preferably from 1 to 10 parts, each
by weight, based on 100 weight parts of siloxane polymer.
In an alternative to the seventh condensation cure system, the
siloxane polymer having at least two hydrolyzable amido groups and,
optionally, other hydrolyzable or condensable group(s) other than
amido bound to silicon atom(s), is reacted with a cross-linker
having, on average, at least two (2.0) hydroxyl groups per molecule
bound to silicon atoms, optionally in the presence of a
condensation catalyst. In a typical preparation, the optional
catalyst would be present in the composition in an amount from 0 to
10 parts, preferably in an amount from 0 to 5 parts, and the
cross-linker, depending on its nature, would be present in an
amount of from 0.1 to 50 parts, preferably in an amount from 1 to
10 parts, each by weight, based on 100 parts by weight of siloxane
polymer.
As a further alternative to the seventh condensation cure system,
siloxane polymer having at least two hydrolyzable amido groups and,
optionally, other hydrolyzable or condensable group(s) other than
amido bound to silicon atom(s), which can be crosslinked,
optionally, in the presence of a condensation catalyst as described
above. In case the siloxane polymer has only two hydrolyzable amido
groups and no further hydrolyzable group(s), the presence of a
cross-linker, which, on average, has at least two (2.0)
hydrolyzable groups per molecule bonded to silicon atom(s), is
required. In case the siloxane polymer has more than two
hydrolyzable amido groups or two amido groups and further
hydrolyzable group(s) other than amido attached to silicon atoms,
the presence of a cross-linker is not required. In a typical
preparation, the optional catalyst would be present in the
composition in an amount from 0 to 10 parts, preferably in an
amount from 0 to 5 parts, and the additional cross-linker, if
required, would be present in an amount of from 0.1 to 20 parts,
preferably in an amount from 0.1 to 10 parts, each by weight, based
on 100 parts by weight of siloxane polymer.
In an eighth condensation cure system useful to the practice of the
present invention, the siloxane polymer, having at least two
hydroxysiloxy groups, is reacted with a cross-linker, having, on
average, at least two (2.0) hydrolyzable ureido groups per molecule
bonded to silicon atom(s), optionally in the presence of a
condensation catalyst. The cross-linker can be an ureido
organosilane (R.sub.n Si(NR'--(CO)--NR".sub.2).sub.4-n), where R,
R' and R" are individually selected from the group consisting of
hydrogen, monovalent hydrocarbon radical or substituted hydrocarbon
radical having less than 7 carbon atoms, functionalized hydrocarbon
radicals, and n either 0 or 1, as described, for example, in U.S.
Pat. No. 3,506, 701, incorporated herein by reference. The
cross-linker may also be a linear or cyclic siloxane oligomer
containing ureidosiloxy groups, a silsesquioxane containing ureido
and, optionally, other hydrolyzable or condensable groups bound
directly to silicon atoms, an organic polymer or resin bearing
ureidosilyl groups and, optionally, an additional crosslinker
having on average at least one other hydrolyzable or condensable
group per molecule other than ureido bound directly to silicon
atom(s) The cross-linker can also be a partial hydrolysis and
condensation product (dimer, trimer, tetramer, etc.) of above
cross-linkers. In a typical preparation, the optional condensation
catalyst would be present in the composition in an amount of from 0
to 10 parts, preferably from 0 to 5 parts, and cross-linker in an
amount of from 0.1 to 50 parts, preferably from 1 to 10 parts, each
by weight, based on 100 weight parts of siloxane polymer.
In an alternative to the eighth condensation cure system, the
siloxane polymer having at least two hydrolyzable ureido groups
and, optionally, other hydrolyzable or condensable group(s) other
than ureido bound to silicon atom(s), is reacted with a
cross-linker having, on average, at least two (2.0) hydroxyl groups
per molecule bound to silicon atoms, optionally in the presence of
a condensation catalyst. In a typical preparation, the optional
catalyst would be present in the composition in an amount from 0 to
10 parts, preferably in an amount from 0 to 5 parts, and the
cross-linker, depending on its nature, would be present in an
amount of from 0.1 to 50 parts, preferably in an amount from 1 to
10 parts, each by weight, based on 100 parts by weight of siloxane
polymer.
As a further alternative to the eighth condensation cure system,
siloxane polymer having at least two hydrolyzable ureido groups
and, optionally, other hydrolyzable or condensable group(s) other
than ureido bound to silicon atom(s), which can be crosslinked,
optionally, in the presence of a condensation catalyst as described
above. In case the siloxane polymer has only two hydrolyzable
ureido groups and no further hydrolyzable group(s), the presence of
a cross-linker, which, on average, has at least two (2.0)
hydrolyzable groups per molecule bonded to silicon atom(s), is
required. In case the siloxane polymer has more than two
hydrolyzable ureido groups or two ureido groups and further
hydrolyzable group(s) other than ureido attached to silicon atoms,
the presence of a cross-linker is not required. In a typical
preparation, the optional catalyst would be present in the
composition in an amount from 0 to 10 parts, preferably in an
amount from 0 to 5 parts, and the additional cross-linker, if
required, would be present in an amount of from 0.1 to 20 parts,
preferably in an amount from 0.1 to 10 parts, each by weight, based
on 100 parts by weight of siloxane polymer.
In a ninth condensation cure system useful to the practice of the
present invention, the siloxane polymer, having at least two
hydroxysiloxy groups, is reacted with a cross-linker, having, on
average, at least two (2.0) hydrolyzable imidato groups per
molecule bonded to silicon atom(s), optionally in the presence of a
condensation catalyst. The cross-linker can be an imidato
organosilane (R.sub.n Si((N.dbd.C(R')(OR")).sub.4-n), where R, R',
and R" are individually selected from the group consisting of
hydrogen, monovalent hydrocarbon radical or substituted hydrocarbon
radical having less than 7 carbon atoms, functionalized hydrocarbon
radicals, and n either 0 or 1, as described, for example, in U.S.
Pat. No. 3,622,529, incorporated herein by reference. The
cross-linker may also be a linear or cyclic siloxane oligomer
containing imidatosiloxy groups, a silsesquioxane containing
imidato and, optionally, an additional crosslinker having on
average at least one other hydrolyzable or condensable groups bound
directly to silicon atoms, an organic polymer or resin bearing
imidatosilyl groups and, optionally, an additional crosslinker
baving on average at least one other hydrolyzable or condensable
group per molecule other than imidato bound directly to silicon
atom(s). The cross-linker can also be a partial hydrolysis and
condensation product (dimer, trimer, tetramer, etc.) of above
cross-linkers. In a typical preparation, the optional condensation
catalyst would be present in the composition in an amount of from 0
to 10 parts, preferably from 0 to 5 parts, and cross-linker in an
amount of from 0.1 to 50 parts, preferably from 1 to 10 parts, each
by weight, based on 100 weight parts of siloxane polymer.
In an alternative to the ninth condensation cure system, the
siloxane polymer having at least two hydrolyzable imidato groups
and, optionally, other hydrolyzable or condensable group(s) other
than imidato bound to silicon atom(s), is reacted with a
cross-linker having, on average, at least two (2.0) hydroxyl groups
per molecule bound to silicon atoms, optionally in the presence of
a condensation catalyst. In a typical preparation, the optional
catalyst would be present in the composition in an amount from 0 to
10 parts, preferably in an amount from 0 to 5 parts, and the
cross-linker, depending on its nature, would be present in an
amount of from 0.1 to 50 parts, preferably in an amount from 1 to
10 parts, each by weight, based on 100 parts by weight of siloxane
polymer.
As a further alternative to the ninth condensation cure system,
siloxane polymer having at least two hydrolyzable imidato groups
and, optionally, other hydrolyzable or condensable group(s) other
than imidato bound to silicon atom(s), which can be crosslinked,
optionally, in the presence of a condensation catalyst as described
above. In case the siloxane polymer has only two hydrolyzable
imidato groups and no further hydrolyzable group(s), the presence
of a cross-linker, which, on average, has at least two (2.0)
hydrolyzable groups per molecule bonded to silicon atom(s), is
required. In case the siloxane polymer has more than two
hydrolyzable imidato groups or two imidato groups and further
hydrolyzable group(s) other than imidato attached to silicon atoms,
the presence of a cross-linker is not required. In a typical
preparation, the optional catalyst would be present in the
composition in an amount from 0 to 10 parts, preferably in an
amount from 0 to 5 parts, and the additional cross-linker, if
required, would be present in an amount of from 0.1 to 20 parts,
preferably in an amount from 0.1 to 10 parts, each by weight, based
on 100 parts by weight of siloxane polymer.
In a tenth condensation cure system useful to the practice of the
present invention, the siloxane polymer, having at least two
hydroxysiloxy groups, is reacted with a cross-linker, having, on
average, at least two (2.0) hydrolyzable alkenoxy groups per
molecule bonded to silicon atom(s), in the presence of a
condensation catalyst. Details of the alkenoxy cure system are
described in U.S. Pat. No. 5,145,901 (incorporated by reference).
The cross-linker may be an alkenoxysilane of the formula R.sub.n
SiX.sub.m Y.sub.4-(n+m), where X is a hydrolyzable or condensable
group other than alkenoxy, and Y is alkenoxy
(--O--CR'.dbd.CR'.sub.2), where n is either 0 or 1, m is either 0
or 1, and R and R' are individually selected from the group
consisting of hydrogen, monovalent hydrocarbon radical or
substituted hydrocarbon radical having less than 7 carbon atoms,
and functionalized hydrocarbon radicals. The cross-linker may also
be a linear or cyclic siloxane or a silsesquioxane containing
alkenoxysiloxy groups and, optionally, an additional crosslinker
having on average at least one other hydrolyzable or condensable
group per molecule other than alkenoxy bound directly to silicon
atoms, an organic polymer or resin bearing alkenoxysilyl groups
and, optionally, other hydrolyzable or condensable groups bound
directly to silicon atom(s). The cross-linker may also be a partial
hydrolysis and condensation product (dimer, trimer, tetramer, etc.)
of above cross-linkers. In a typical preparation, the catalyst
would be present in the composition in an amount of from 0.01 to 10
parts, preferably in an amount of from 0.01 to 5 parts, and
cross-linker in an amount of from 0.1 to 50 parts, preferably in an
amount from 1 to 10 parts, each by weight, based on 100 weight
parts of siloxane polymer.
In an alternative to the tenth condensation cure system, the
siloxane polymer having at least two hydrolyzable alkenoxy groups
and, optionally, other hydrolyzable or condensable group(s) other
than alkenoxy bound to silicon atom(s), is reacted with a
cross-linker having, on average, at least two (2.0) hydroxyl groups
per molecule bound to silicon atoms, in the presence of a
condensation catalyst. In a typical preparation, the catalyst would
be present in the composition in an amount from 0.01 to 10 parts,
preferably in an amount from 0.01 to 5 parts, and the cross-linker,
depending on its nature, would be present in an amount of from 0.1
to 50 parts, preferably in an amount from 1 to 10 parts, each by
weight, based on 100 parts by weight of siloxane polymer.
As a further alternative to the tenth condensation cure system,
siloxane polymer having at least two hydrolyzable alkenoxy groups
and, optionally, other hydrolyzable or condensable group(s) other
than alkenoxy bound to silicon atom(s), which can be crosslinked,
in the presence of a condensation catalyst as described above. In
case the siloxane polymer has only two hydrolyzable alkenoxy groups
and no further hydrolyzable group(s), the presence of a
cross-linker, which, on average, has at least two (2.0)
hydrolyzable groups per molecule bonded to silicon atom(s), is
required. In case the siloxane polymer has more than two
hydrolyzable alkenoxy groups or two alkenoxy groups and further
hydrolyzable group(s) other than alkenoxy attached to silicon
atoms, the presence of a cross-linker is not required. In a typical
preparation, the catalyst would be present in the composition in an
amount from 0.01 to 10 parts, preferably in an amount from 0.01 to
5 parts, and the additional cross-linker, if required, would be
present in an amount of from 0.1 to 20 parts, preferably in an
amount from 0.1 to 10 parts, each by weight, based on 100 parts by
weight of siloxane polymer.
In a eleventh condensation cure system useful to the practice of
the present invention, the siloxane polymer having at least two
hydroxysiloxy groups, is reacted with a cross-linker, having, on
average, at least two (2.0) hydrolyzable isocyanato per molecule
groups bonded to silicon atom(s), in the presence of a condensation
catalyst. The cross-linker may be a isocyanato organosilane of the
formula R.sub.n Si(OR').sub.m (NCO).sub.4-(m+n), as described in
German Patent No. 2,653,498 and Japanese Patent No. 57,168,946,
both patents being incorporated herein by reference, where R is
hydrogen, monovalent hydrocarbon radical or substituted hydrocarbon
radical having less than 7 carbon atoms, functionalized hydrocarbon
radicals, nitrogen compounds of the formula --N.dbd.CR".sub.2 or
--NR"COR" or --NR".sub.2 or --NR'", R' is monovalent hydrocarbon or
substituted hydrocarbon radicals having less than 7 carbon atoms,
R' is either hydrogen, monovalent hydrocarbon radicals having less
than 7 carbon atoms, R'" is cycloalkyl radical, and n is either 0
or 1, and m is either 0, 1 or 2. The cross-linker may also be a
linear or cyclic siloxane oligomer containing isocyanatosiloxy
groups, a silsesquioxane containing isocyanato and, optionally, an
additional crosslinker having on average at least one other
hydrolyzable or condensable group per molecule other than
isocyanato bound directly to silicon atoms, an organic polymer or
resin bearing isocyanatosilyl groups and, optionally, other
hydrolyzable or condensable groups bound directly to silicon
atom(s). The cross-linker may also be a partial hydrolysis and
condensation product (dimer, trimer, tetramer, etc) of above
cross-linkers. In a typical preparation, the condensation catalyst
would be present in the composition in an amount of 0.01 to 10
parts, preferably in an amount of from 0.01 to 5 parts, the
cross-linker would be present in an amount of from 0.1 to 50 parts,
preferably in an amount from 1 to 10 parts, each by weight, based
on 100 weight parts of siloxane polymer.
In an alternative to the eleventh condensation cure system, the
siloxane polymer having at least two hydrolyzable isocyanato groups
and, optionally, other hydrolyzable or condensable group(s) other
than isocyanato bound to silicon atom(s), is reacted with a
cross-linker having, on average, at least two (2.0) hydroxyl groups
per molecule bound to silicon atoms, in the presence of a
condensation catalyst. In a typical preparation, the catalyst would
be present in the composition in an amount from 0.01 to 10 parts,
preferably in an amount from 0.01 to 5 parts, and the cross-linker,
depending on its nature, would be present in an amount of from 0.1
to 50 parts, preferably in an amount from 1 to 10 parts, each by
weight, based on 100 parts by weight of siloxane polymer.
As a further alternative to the eleventh condensation cure system,
siloxane polymer having at least two hydrolyzable isocyanato groups
and, optionally, other hydrolyzable or condensable group(s) other
than isocyanato bound to silicon atom(s), which can be crosslinked,
in the presence of a condensation catalyst as described above. In
case the siloxane polymer has only two hydrolyzable isocyanato
groups and no further hydrolyzable group(s), the presence of a
cross-linker, which, on average, has at least two (2.0)
hydrolyzable groups per molecule bonded to silicon atom(s), is
required. In case the siloxane polymer has more than two
hydrolyzable isocyanato groups or two isocyanato groups and further
hydrolyzable group(s) other than isocyanato attached to silicon
atoms, the presence of a cross-linker is not required. In a typical
preparation, the catalyst would be present in the composition in an
amount from 0.01 to 10 parts, preferably in an amount from 0.01 to
5 parts, and the additional cross-linker, if required, would be
present in an amount of from 0.1 to 20 parts, preferably in an
amount from 0.1 to 10 parts, each by weight, based on 100 parts by
weight of siloxane polymer.
In a twelfth condensation cure system useful for the practice of
this invention, the siloxane polymer, having at least two
hydroxysiloxy or alkoxysiloxy groups, is reacted with a
cross-linker, bearing, on average, at least two (2.0) reactive
silanol groups, in presence of a condensation catalyst. The
cross-linker is selected from the group consisting of silica,
silicate, siliconate, silanolate, silanol functional silicone
resins, and silanol functional organic resins. Siliconates and
silanolates useful for this invention can be represented by the
formulae RSi(O.sup.- M.sup.+).sub.n (OH).sub.3-n and R.sub.2
Si(OM).sub.m (OH).sub.2-m, respectively, where R is monovalent
hydrocarbon radical, substituted hydrocarbon radical having less
than 7 carbon atoms, or functionalized hydrocarbon radical, and M
is selected from the group consisting of an alkali metal cation, an
ammonium group, and a phosphonium group, and n is an integer or
fraction having value of from 0.1 to 3, and m is an integer or
fraction having a value of from 0.1 to 2. The cross-linker may also
be a partial condensation product (dimer, trimer, tetramer, etc) of
the above cross-linkers. Crosslinking of hydroxysiloxy endblocked
siloxanes with siliconates of formula RSi(O.sup.- M.sup.+).sub.m
(OH).sub.3-m in emulsions is described, for example, in U.S. Pat.
No. 4,816,506, incorporated herein by reference. After the high
solids gel consisting of hydroxysiloxy endblocked siloxane,
surfactant and water, is formed, a cross-linker selected from the
group consisting of silica, silicate, siliconate, silanolate,
silanol functional organic resin or silicone resin, and a
condensation catalyst, such as dibutyltindilaurate, are added to
the emulsion. This type of crosslinking reaction is well known in
the art, and described in U.S. Pat. Nos. 4,221,688, 4,244,849,
4,273,813, 5,004,771, 3,355,406, which are incorporated herein by
reference. In a typical preparation, the condensation catalyst
would be present in the composition in an amount of from 0.01 to 10
parts, preferably in an amount of from 0.01 to 5 parts, and the
cross-linker would be present in an amount of from 0.1 to 50 parts,
preferably in an amount from 1 to 30 parts, each by weight, based
on 100 weight parts of siloxane polymer.
The crosslinker(s) or cure by-product(s) of certain condensation
cure systems can act as catalyst or co-catalyst to other
condensation cure systems. Examples of such co-catalysis are a
mixture of silazane crosslinker and oximosilane crosslinker or a
silane crosslinker which bears both amino and oximo
functionalities, as described in U.S. Pat. Nos. 3,742,004,
3,758,441 and 4,191,817. Both systems are capable of crosslinking
hydroxysiloxy functional organic polymer without the presence of a
further catalyst. Another example is a silane bearing both amino
and alkoxy functionalities, such as in CH.sub.3 (C.sub.2 H.sub.5
O)Si(NHCH.sub.2 CH.sub.2 CH.sub.2 Si(OC.sub.2
H.sub.5).sub.3).sub.2, disclosed in U.S. Pat. No. 4,458,055,
incorporated herein by reference. Another example of such
co-catalysis is the condensation reaction between an alkoxysilane
and a hydroxysiloxy functional organic polymer, or between two
alkoxysiloxy functional organic polymers, catalyzed by an
acetoxysilane crosslinker in presence of a primary tin condensation
catalyst, as described in U.S. Pat. Nos. 3,293,204 and 4,515,932,
as well as in "Bifunctional catalysis in the condensation of
silanols and alkoxysilanes" by Hsien-Kun Chu, Robert P. Cross, and
David I. Crossan in Journal of Organometallic Chemistry, 425
(1992), pages 9-17. Combining various condensation cure
chemistries, thus, may be advantageous.
The following class of cure systems that do not generate volatile
by-products ("tethered leaving groups") is useful in the practice
of the current invention.
In the first non-volatile cure system useful for the practice of
this invention, the siloxane polymer has at least two hydroxysiloxy
groups, and the cross-linker has, on average, at least two (2.0)
silacycloalkane groups per molecule. The siloxane polymer and the
cross-linker are reacted in the presence of a nucleophilic
catalyst, such as an amine, a hydroxyl amine, a guanidine, a
N-alkylated guanidine, an urea, or a N-alkylated urea. The
preferred catalyst is a dialkylhydroxylamine. The most preferred
catalyst is diethylhydroxylamine. The silacycloalkane cure system
is described in detail in U.S. Pat. Nos. 4,965,367, 4,985,568,
5,001,187, 5,049,688, 5,110,967, and European Patent Nos. 0,423,684
and 0,423,685, all patents being incorporated herein by reference.
The cross-linker can be a compound bearing silacycloalkane groups
--(Si(CH2)n). the preferred cross-linker is a compound bearing
silacyclobutane groups. The silacycloalkane group(s) may be
attached to the cross-linker via Si--C, Si--(O--Si).sub.n --Si, or
Si--(O--Si).sub.n --C bonds, wherein n is a positive integer. The
cross-linker may also be a linear or cyclic siloxane containing
silacycloalkane radicals, a silsesquioxane containing
silacycloalkane radicals, an organic oligomer, polymer or resin
bearing silacycloalkane groups directly bound to silicon or carbon
atom(s). In a typical preparation, the catalyst would be present in
the composition in an amount of from 0.01 to 10 parts, preferably
in an amount of from 0.1 to 5 parts, and the cross-linker would be
present in an amount of from 0.1 to 50 parts, preferably in an
amount from 1 to 10 parts, each by weight, based on 100 parts by
weight of siloxane polymer.
In an alternative to the first non-volatile cure system, the
siloxane polymer has at least two silacycloalkane groups. The
polymer is then reacted in the presence of a nucleophilic catalyst,
as described above, with a cross-linker having, on average, at
least two hydroxyl groups per molecule bound to silicon atoms. In a
typical preparation, the catalyst would be present in the
composition in an amount from 0.01 to 10 parts, preferably in an
amount from 0.1 to 5 parts, and the cross-linker, depending on its
nature, would be present in an amount of from 0.1 to 50 parts,
preferably in an amount from 1 to 10 parts, each by weight, based
on 100 parts by weight of siloxane polymer.
In a further alternative to the first non-volatile cure system, the
siloxane polymer having at least two silacycloalkane groups and,
optionally, other hydrolyzable or condensable group(s) other than
silacycloalkane bound to silicon atoms, which can be crosslinked in
the presence of a nucleophilic catalyst, as described above. In
case the polymer has only two silacycloalkane groups and no further
hydrolyzable group(s), the presence of a cross-linker, which, on
average, has at least two (2.0) hydrolyzable groups per molecule
bonded to silicon atom(s), is required. In case the polymer has
more than two silacycloalkane groups or two silacycloalkane groups
and further hydrolyzable group(s) attached to silicon atoms, the
presence of a cross-linker is not required. In a typical
preparation, the catalyst would be present in the composition in an
amount from 0.01 to 10 parts, preferably in an amount from 0.1 to 5
parts, and the additional cross-linker, if required, would be
present in an amount of from 0.1 to 20 parts, preferably in an
amount from 0.1 to 10 parts, each by weight, based on 100 parts by
weight of siloxane polymer.
In the second non-volatile cure system useful to the practice of
the present invention, the siloxane polymer having at least two
hydroxysiloxy groups, is reacted with a cross-linker having, on
average, at least two (2.0) aza-silacycloalkane groups, in the
presence of a condensation catalyst. The aza-silacycloalkane cure
system is described in detail in U.S. Pat. Nos. 5,136,064,
5,238,988, 5,239,099, 5,254,645, and World Patent No. 94/14820, all
patents being incorporated herein by reference The cross-linker can
be a compound bearing aza-silacyclopentane groups attached via the
silicon or nitrogen atom. The preferred cross-linker is a compound
bearing aza-silacyclopentane groups. The cross-linker may also be a
linear or cyclic siloxane, a silsesquioxane, an organic oligomer,
polymer or resin, bearing aza-silacycloalkane radicals. In a
typical preparation, the catalyst would be present in the
composition in an amount of from 0.01 to 10 parts, preferably in an
amount of from 0.1 to 5 parts, and the cross-linker would be
present in an amount of from 0.1 to 50 parts, preferably in an
amount from 1 to 10 parts, each by weight, based on 100 parts by
weight of siloxane polymer.
In an alternative to the second non-volatile cure system, the
siloxane polymer has at least two aza-silacycloalkane groups,
attached to the polymer either via the silicon or nitrogen atom The
polymer is then reacted in the presence of a condensation catalyst,
as described above, with a cross-linker having, on average, at
least two (2.0) hydroxyl groups bound to silicon atoms In a typical
preparation, the catalyst would be present in the composition in an
amount from 0.01 to 10 parts, preferably in an amount from 0.1 to 5
parts, and the cross-linker, depending on its nature, would be
present in an amount of from 0.1 to 50 parts, preferably in an
amount from 1 to 10 parts, each by weight, based on 100 parts by
weight of siloxane polymer.
As a further alternative to the second non-volatile cure system,
the siloxane polymer having at least two aza-silacycloalkane
groups, bound to the polymer via either the silicon or nitrogen
atom, and, optionally, other hydrolyzable or condensable group(s)
other than aza-silacycloalkane bound to silicon atom(s), can be
crosslinked in the presence of a condensation catalyst, as
described above. In case the polymer has only two
aza-silacycloalkane groups and no further hydrolyzable group(s)
attached to silicon atoms, the presence of a cross-linker, which,
on average, has at least two (2.0) hydrolyzable groups per molecule
bonded to silicon atom(s), is required. In case the polymer has
more than two aza-silacycloalkane groups or two aza-silacycloalkane
groups and further hydrolyzable group(s) attached to silicon
atom(s), the presence of a cross-linker is not required. In a
typical preparation, the catalyst would be present in the
composition in an amount from 0.01 to 10 parts, preferably in an
amount from 0.1 to 5 parts, and the additional cross-linker, if
required, would be present in an amount of from 0.1 to 20 parts,
preferably in an amount from 0.1 to 10 parts, each by weight, based
on 100 parts by weight of siloxane polymer.
Another class of silicon cure systems involves addition
(hydrosilylation) reactions between a siliconhydride (Si--H) group
and an alkenyl group (--(CH.sub.2).sub.n --CH.dbd.CH.sub.2) group.
The silicon hydride group may be attached either to the polymer or
the cross-linker The alkenyl group may be attached either to the
polymer or the cross-linker. If the alkenyl group is attached to
the crosslinker, the crosslinker may be organic, silicon modified
organic, or siloxane in nature.
The number of reactive radicals on the polymer and the cross-linker
determine, whether a cured elastomer is obtained. An elastomeric
network is being formed by the addition cure, if the sum of the
reactive radicals on the polymer and the reactive radicals on the
cross-linker is at least 5. For example, if the polymer has two
alkenyl groups and the cross-linker has three silicon hydride
groups an elastomer is obtained.
The addition cure chemistry requires a catalyst to effect the
reaction between polymer and crosslinking compound. Suitable
hydrosilylation catalysts are well know in the art. Examples of
suitable catalysts preferably employed in the addition reactions
(a) to (c) are group VIII transition metal (noble metal) compounds
The noble metal catalyst is selected from any of those well known
to the art, such as those described in U.S. Pat. No. 3,923,705,
said patent being hereby incorporated by reference to show platinum
catalysts. A preferred platinum compound catalyst is a composition
consisting essentially of the reaction product of chloroplatinic
acid and an organosilicon compound containing terminal aliphatic
unsaturation, such as described in U.S. Pat. No. 3,419,593, said
patent being incorporated by reference. When said noble metal
catalysts are used, they are added in an amount from 0.000001 to
0.5 parts, preferably from 0.00001 to 0.02, and more preferably
from 0.00001 to 0.002 weight parts, per 100 weight parts of the
silicon modified organic polymer.
In the first addition cure system useful to the practice of the
present invention, the siloxane polymer bearing alkenyl groups, is
reacted with a crosslinker, having, on average, at least two (2.0)
silicon-bonded hydrogen atoms per molecule, the reaction occurring
in the presence of a hydrosilylation catalyst. Details of this cure
system are taught in U.S. Pat. No. 4,248,751 which is incorporated
herein by reference. The siloxane polymer contains at least one
alkenyl group. However, in order to obtain sufficient curability,
it is desirable that the siloxane polymer contains at least 1.1,
more preferably from 1.5 to 4 reactive alkenyl groups. The silicon
hydride cross-linker can be chosen from hydrolyzable silicon
hydride, polymeric or oligomeric compounds, containing, on average,
at least two (2.0) hydrogen-silicon bonds and optionally
hydrolyzable or condensable groups bound directly to silicon atoms,
such as polyorganohydrogensiloxane, alkylhydrogencyclosiloxane, and
liquid copolymers comprising SiO.sub.2 and/or SiO.sub.3/2 units and
bearing silicon-bonded hydrogen radicals such as taught in U.S.
Pat. No. 4,310,678. The silicon hydride cross-linker can also be
chosen from organic polymers and resins bearing Si--H groups. The
cross-linker may also be a silsesquioxane containing hydrogen and
optionally also alkoxy groups bound directly to silicon atoms, as
described, for example, in U.S. Pat. No. 5,047,492, incorporated
herein by reference. Examples of cross-linkers are trimethylsilyl
endblocked polymethylhydrogensiloxane and
methylhydrogencyclosiloxane. The SiH functional cross-linker is
added in sufficient amount to provide at least one hydrogen atom
for each vinyl group in the polydiorganosiloxane polymer.
Preferably, an excess of SiH functional cross-linker is provided so
that all vinyl groups can be reacted. In a typical preparation, the
catalyst would be present in the composition in an amount of from
0.000001 to 0.5 parts, preferably from 0.00001 to 0.02 parts, and
silicon hydride cross-linker, depending on its nature, in an amount
of from 0.1 to 10 parts, each by weight, of siloxane polymer.
In an alternative to the first addition cure system, the
hydrosilylation reaction takes place, in presence of a
hydrosilylation catalyst, between a siloxane polymer having
silicon-hydrogen bonds and a crosslinker having alkenyl groups
attached to silicon or carbon atoms(s) The siloxane polymer
contains at least one silicon-hydrogen bond. However, in order to
obtain sufficient curability, it is desirable that the siloxane
polymer contains at least 1.1, more preferably from 1.5 to 4
reactive silicon-hydrogen bonds. The cross-linker has, on average,
at least two (2.0) alkenyl groups per molecule directly attached to
at least one silicon atom, and can be selected from the group
consisting of trisalkenylsilanes, alkenyl functional linear or
cyclic siloxanes, liquid copolymers comprising SiO.sub.2 and/or
SiO.sub.3/2 units and bearing silicon bonded alkenyl groups,
silsesquioxane containing alkenyl and optionally hydrolyzable or
condensable groups, that do not interfere with the noble metal
catalyzed cure and are bound directly to silicon atoms, organic
polymers or resins having alkenylsilyl groups and optionally
hydrolyzable or condensable silyl groups, that do not interfere
with the noble metal catalyzed cure bound directly to carbon
atom(s) via Si--C bonds, or organic oligomers, polymers or resins
bearing alkenyl groups. The cross-linker is added to the
composition in such an amount as to provide at least one hydrogen
atom on the siloxane polymer for each alkenyl in the cross-linker.
In a typical preparation, the catalyst would be present in the
composition in an amount of from 0.000001 to 0.5 parts, preferably
from 0.00001 to 0.02 parts, and silicon hydride cross-linker,
depending on its nature, in an amount of from 0.1 to 10 parts, each
by weight, of siloxane polymer.
In another class of cure systems useful in the practice of the
present invention, the crosslinking between Si--C bonds occurs via
free radical reactions. In one example of this cure system a
stabilized emulsion of hydroxysiloxy or trimethylsiloxy endblocked
siloxane in water is reacted with siloxane containing sufficient
alkenyl substituted siloxane units to facilitate the crosslinking
using a peroxide or other free radical initiator, or high energy
radiation, as described in U.S. Pat. No. 4,273,634 which is
incorporated herein by reference. In a typical preparation, the
free radical initiator would be present in the composition in an
amount of from 0.01 to 10 parts by weight of siloxane polymer.
The following class of miscellaneous organic cure systems is useful
to the practice of the current invention.
In the first organic cure system useful to the practice of the
present invention, the siloxane polymer, bearing at least two
carboxyalkylsiloxy groups, is reacted with a cross-linker, having,
on average, at least two epoxide groups; the reaction occurring in
presence of a catalyst, as disclosed in U.S. Pat. No. 4,623,694,
incorporated herein by reference. The cross-linker can be an
epoxide compound selected from the group consisting of diglycidyl
ethers of di- and bis-phenols. The catalyst is selected from the
group consisting of (organo)metallic compounds, amino compounds,
salts of amino compounds, or mixtures of catalysts. In a typical
preparation, the catalyst would be present in the composition in an
amount of 0.01 to 10 parts, preferably in an amount of from 0.01 to
5 parts, and the cross-linker would be present in an amount of from
2 to 100 parts, preferably in an amount from 5 to 50 parts, each by
weight, based on 100 weight parts of siloxane polymer.
In another organic cure system useful to the practice of the
present invention, the siloxane polymer, bearing at least two
primary or secondary aminosiloxy groups, is reacted with a
cross-linker, having, on average, at least two carboxylic anhydride
groups; and the reaction optionally occurring in the presence of an
acrylating agent, as disclosed in German Patent No. 4,211,256,
incorporated herein by reference. The cross-linker is either an
alkoxysilane, an alkoxysiloxane, or an alkoxysiloxy or alkoxysilyl
functional resin, or a siloxane containing carboxylic anhydride
groups. Depending on the number of amino and carboxy groups
involved in the reaction, in a typical preparation the catalyst
would be present in the composition in an amount of 0.01 to 5
parts, preferably in an amount of from 0.05 to 2 parts, the
cross-linker would be present in an amount of from 0.1 to 100
parts, preferably in an amount from 1 to 50 parts, each by weight,
based on 100 weight parts of siloxane polymer.
Fillers
Fillers may be optionally added to the composition of the
invention. Depending on the type of filler under consideration and
the intended purpose of the filler addition, the filler may be
added to the initial mixture of siloxane polymer, surfactant, and
water, optionally also containing cross-linker and catalyst and
optional formulation ingredients; it may be added after the initial
emulsification step to the high solids gel phase; or it may be
added to the silicone latex dispersion after dilution with water.
The filler may be added neat (dry) or as a dispersion (slurry) in
water, siloxane polymer, polymer/mixture, solvent/polymer mixture,
solvent, or other suitable media. Fillers may be added for
reinforcing or extending (cheapening) the cured elastomer, or for
achieving special performance characteristics of the wet silicone
latex dispersion or the cured elastomer, exemplified, but not
limited to, such properties as handling characteristics, electrical
conductivity, fire resistance, self-extinguishing feature,
radiation shielding, or changes in the surface appearance or
characteristics of the. Any filler which does not react with the
silicone emulsion or silicone latex dispersion is suitable.
Fillers added for extending or reinforcing purposes typically have
an average particle size below 10 micrometers, preferably below 2
micrometers, and are added at 10 to 200 weight parts, preferably 40
to 120 weight parts, per 100 weight parts of siloxane polymer.
Examples of such fillers are aluminum oxide, hydrated aluminum
hydroxide, diatomaceous earths, magnesium hydroxide, ground quartz,
mica, calcium carbonate, clay, barium sulfate, zinc oxide, iron
oxide, and talcum. If necessary, liquid alkoxy silanes which are
soluble in the siloxane polymer may be added with the filler to
compatibilize the filler with the siloxane polymer.
Various pigments, such as carbon black or titanium dioxide, may
also be added as fillers. Since these fillers are only intended to
affect the color of the cured silicone latex elastomer, they are
typically added at 0.1 to 20 weight parts, preferably from 0.5 to
10 weight parts, per 100 weight parts of siloxane polymer. Titanium
dioxide has been found to be particularly useful as an ultraviolet
light screening agent.
It should be noted that selection and addition to the composition
of particular fillers, may improve the physical properties of the
resulting elastomer, particularly tensile property, elongation
property, hardness and heat stability Precipitated or fumed silicas
may be used as reinforcing fillers. The silicone latex dispersions
of this invention which are cured with catalysts other than Sn(IV)
compounds are particularly useful, because they can be reinforced
with colloidal silicas without negatively effecting the shelf-life
of the wet latex dispersion and/or the durability of the cured
elastomer. Although common fumed and precipitated silicas can be
used, colloidal silicas are much more effective in reinforcing the
cured silicone latex elastomers. Aqueous dispersions of fumed or
precipitated colloidal silicas are commercially available. Stable
dispersions of fumed silica in water are available at a pH varying
from 5 to 11. The amount of fumed silica in the dispersion varies
from about 10 to about 30 percent by weight. Such fumed silica
dispersions are available from CABOT Corporation under the
trademark Cab-o-Sphere (R). The dispersions are stated to be
stabilized with ammonia, sodium or potassium hydroxide. The above
described dispersions of fumed silica are different from the
aqueous sodium, ammonium, or aluminum ion stabilized sols of
colloidal silica, such as described in U.S. Pat. No. 4,221,688. The
colloidal silicas sols are commercially available from NALCO
Chemical Company (Naperville, Ill.). Use of fumed silica
dispersions and colloidal silica sols for reinforcement of silicone
latex dispersions are described in U.S. Pat. Nos. 5,162,429 and
5,321,075, incorporated herein by reference. Elastomers made from
silicone latices cured with catalysts other than Sn(IV); stabilized
with surfactants, which are not or do not form species capable of
catalyzing siloxane redistribution/degradation reactions, even when
exposed to temperatures above 100 C; and containing ammonium
stabilized silicas are heat stable up to temperatures of 200 C
(long-term) and 250 C (short term). Elastomers made from silicone
latex dispersions containing sodium stabilized silicas are not heat
stable at temperatures above 120 C (short term) and 150 C
(long-term). Acidic silicas (those containing H+ as a stabilizer),
also yield heat stable elastomers. In general, colloidal or
dispersed silicas which are not stabilized by Group Ia or IIa
elements, yield heat stable elastomers. It is anticipated that
silicas stabilized with other volatile bases, such as volatile
organic amines, should provide similar heat stability of the
silicone latex elastomer as achieved with ammonium stabilized
colloidal or dispersed silicas. Suitable organic amines are of the
formulae (R).sub.3-x N(H)x, where x=0, 1, 2, or 3, R is alkyl or
aryl group, such as in N(CH.sub.2 CH.sub.2 OH).sub.3 or NH(CH.sub.2
CH.sub.2 OH).sub.2. The volatile organic amines include
cyclohexylamine, triethylamine, dimethylaminomethylpropanol,
diethylaminoethanol, aminomethyl propanol, amino butanol,
monoethanolamine, monoisopropanolamine, dimethylethanolamine,
diethanolamine, aminoethylpropanediol, aminomethylpropanediol,
diisopropanolamine, morpholine, tris(hydroxymethyl)aminomethane,
triisopropanolamine, triethanolamine, aniline, and urea.
Non-siliceous filler are preferably used in silicone latex
dispersions of this invention cured with Sn(IV) compounds as
catalyst, since they do not negatively affect the shelf-life of the
wet latex dispersion and/or the durability of the cured elastomer.
Precipitated surface treated calcium carbonates can be used as
semi-reinforcing fillers, ground calcium carbonates, either treated
or untreated, can be used as extending fillers.
Fillers which may be used to modify the surface appearance of the
cured silicone latex elastomer and/or to improve the workability of
the wet latex dispersion include fibers of 0.1 to 100 millimeters
length. The fiber may be selected from the group consisting of
natural fibers, regenerated fibers, and synthetic fibers. Natural
fibers include pulp, cotton, flax, silk, and wool. Regenerated
fibers are such as rayon. Synthetic fibers include nylon and
polyester.
Fillers which may be used to achieve fire retardency or fire
resistance of the cured silicone latex elastomer include aluminum
hydroxide (trihydrate), non-flammable fibers, ceramic or glass
fibers or microspheres, and vermiculite, as described in U.S. Pat.
No. 4,719,251, incorporated herein by reference.
Fillers which may be used to achieve electric conductivity of the
cured silicone latex elastomer include carbon black, metal coated
ceramic spheres or fibers, metal coated glass spheres or fibers,
uncoated or metal coated graphite fibers or spheres as disclosed in
U.S. Pat. Nos. 4,545,914 and 4,547,312, incorporated herein by
reference.
Resin Reinforces
The silicone latex dispersion of this invention can also be
reinforced with silsesquioxanes, for instance a
methylsilsesquioxane having the unit formula RSiO.sub.3/2, which is
prepared in an emulsion. The process of making these
silsesquioxanes, having colloidal sized particles is found in U.S.
Pat. No. 3,433,780, incorporated herein by reference. The
silsesquioxanes can be employed in the form of colloidal
suspensions, which are added to the silicone emulsion (made from
siloxane polymer, surfactant, and water) or the crosslinked latex
(made from siloxane polymer, surfactant, cross-linker, water, and,
if required, catalyst). Copolymers and blends of the
silsesquioxanes can be employed as well as the individual ones and
the formula RSiO.sub.3/2 is intended to include all such
materials.
Catalyst Deactivation
For certain condensation cure chemistries and compositions in which
the catalyst remains active and negatively affects shelf-life of
the wet dispersion and/or durability of the cured elastomer, it may
be desirable to add compounds to the instant composition that
deactivate (poison) the catalyst after the cure have sufficiently
progressed. In this process, a sufficient "gestation time" of
typically several days needs to be allowed before the catalyst can
be quenched. Deactivation of Sn(IV) catalysts with alkyl mercaptan,
8-quinolinol, thio glycolic acid, and salts of thio glycolic acid
has been disclosed in U.S. Pat. No. 4,609,486, incorporated herein
by reference.
Stabilizers
For certain condensation cure chemistries and compositions in which
the catalyst remains active and negatively affects shelf-life of
the wet dispersion, it may be desirable to add compounds to the
instant composition that act as shelf life stabilizers. Amine
compounds, such as diethylamine, hydroxylamine, or
2-amino-2-methyl-1-propanol have been found to improve the shelf
life (stability of properties) of the wet silicone latex
dispersions containing Sn(IV) catalysts and silicas. The preferred
shelf life stabilizer is 2-amino-2-methyl-1-propanol, as disclosed
in U.S. Pat. Nos. 4,427,811 and 4,608,412, incorporated herein by
reference.
Other Additives
The silicone latex dispersion of the present invention may contain
additional ingredients to further modify the properties of the
latex dispersion or the cured elastomeric products obtained from
the latex dispersion. For example, antifoams, dispersants, or
freeze/thaw stabilizers may be added to the dispersion.
Articles, Uses
The silicone latex dispersions can be applied as sealants, putties,
molding materials, or foams. The evaporation of water from the
dispersion normally occurs by unattended exposure to the ambient
atmosphere. The evaporation may be additionally assisted by a flow
of dry air or other gas, either at ambient temperature or at
elevated temperatures, by infrared heating, micro-waving, or a
combination of various means. Care should be taken when accelerated
means are used to evaporate the aqueous phase that the rapidly
leaving water vapor does not produce undesired discontinuities in
the cured product.
EXAMPLES
The following examples are presented to further illustrate the
compositions of this invention, but are not to be construed as
limiting the invention, which is delineated in the appended claims.
In the following examples, the aforesaid wet dispersions were cast
into films one day after the dispersions were made, and the film
was allowed to dry for a minimum of seven days prior to testing.
Durometer results were obtained by the method described in ASTM
C661 "Indentation Hardness of Elastomeric-Type Sealants by Means of
a Durometer". Tensile and elongation results were obtained by the
method described in ASTM D412 "Vulcanized Rubber and Thermoplastic
Rubbers and Thermoplastic Elastomers-Tension" using dumbbell
specimens with an L dimension equal to 0.5 inch.
Example 1
Using parts by weight based on siloxane polymer, 100 parts of
50,000 cs (110,000 Mw) --OH endblocked polydimethylsiloxane
("PDMS") and 4 parts of a 50/50 by weight mixture of water and
Tergitol TMN-6 surfactant, an ethoxylated trimethylnonanol, were
mixed in a laboratory mixer (Whip Mix) until a very high solids gel
emulsion was formed. The aqueous Tergitol TMN-6 solution had a
viscosity of 0.082 Pa-s at a shearing gradient of 1 sec.sup.-1 as
measured on a Brookfield viscometer (Brookfield Engineering
Laboratories, Inc, Stoughten, Mass. The emulsion was diluted with
water to 95% silicone polymer solids. This process was repeated
with final dilutions of 90, 85, 80, 75, and 70% silicone polymer
solids being prepared 0.2 parts dibutyltindilaurate catalyst and
0.8 part isobutyltrimethoxysilane were mixed in to each of these
emulsions. The formulations were transferred to a semkit cartridge
(Courtaulds Aerospace, Indianapolis, Ind.) and left to stand
overnight. The next day a small amount of each sample was spread
out to dry. The extrusion rate was measured by extruding the sample
from the semkit through a 1/8" orifice at a constant pressure of 32
psi and weighing the amount extruded. A tack-free elastomer
remained after the evaporation of water.
______________________________________ % Si Polymer Extrusion rate
solids (grams per minute) ______________________________________ 95
3.9 90 19.8 85 222.2 80 1228.8 75 4376.1 70 6193.5
______________________________________
Example 2
Using parts by weight based on siloxane polymer, 2 parts of a 50%
aqueous solution of sodium lauryl sulfate was mixed into 100 parts
of 50,000 cs (Mw 110,000) --OH endblocked PDMS polymer in a
laboratory mixer (Whip mix) (Whip Mix Corporation, Louisville,
Ky.). This emulsion gel was diluted with 20.25 parts of water. 0.42
parts of stannous octoate, 0.96 parts of
chloropropyl-trimethoxysilane, and 0.52 parts of
2-amino-2-methyl-1-propanol (95% solution) were mixed sequentially
into the emulsion. This dispersion has good handling properties.
Specifically, this dispersion exhibited greater resistance to
extrusion and tooling than a 75% solids silicone dispersion
prepared from a crosslinked emulsion polymer. It formed a silicone
elastomer after water evaporation with a tensile strength of 75 psi
and an elongation of 1929%.
Example 3
11.2 parts of a 50/50 solution of sodium lauryl sulfate and water
was added to 100 parts of a 60,000 mPa.s trimethoxysilane
endblocked PDMS polymer in a laboratory mixer (Whip mix). The
ingredients were mixed until a high solids emulsion gel was formed.
An additional 13 parts of water and 0.5 parts of Cotin S-10
stannous octoate were mixed in. This dispersion had good handling
properties and formed a silicone elastomer after water evaporation.
Specifically this dispersion exhibited greater resistance to
extrusion and tooling than a 75% solids silicone dispersion
prepared from a crosslinked silicone emulsion polymer.
Example 4
Using parts by weight based on siloxane polymer, 6.2 parts of Makon
10, an alkylphenoxy polyoxyethylene ethanol, nonionic surfactant
and 3.0 parts of water were added to 100 parts of 50,000 cs (Mw
110,000) --OH endblocked PDMS polymer. The aqueous Makon 10
solution had a viscosity of 5.35 Pa-s at a shearing gradient of 1
sec.sup.-1 as measured on a Brookefield viscometer (Brookfield
Engineering Laboratories, Inc., Stoughten, Mass. In a laboratory
mixer (whip mix) these ingredients were mixed until a very high
solids emulsion gel was formed. This gel was diluted with 9.10
parts water. 0.58 parts stannous octoate and 0.92 parts
chloropropyltrimethoxysilane were mixed into the emulsion 2.0 parts
of 15% NH4OH water solution was added after no more than a 10
minute gestation time. This emulsion had good handling properties
and formed a silicone elastomer after water evaporation.
Specifically this dispersion exhibited greater resistance to
extrusion and tooling than a 75% solids silicone dispersion
prepared from a crosslinked silicone emulsion polymer.
Example 5
Using parts by weight based on siloxane polymer, 0.84 parts
isobutyltrimethoxysilane, 1.0 part dibutyltindiacetate and 100
parts of 50,000 cs (Mw 110,000) --OH endblocked PDMS polymer were
mixed together in a laboratory mixer (Whip mix). 3.04 parts water
and 6.10 parts Makon 10 nonionic surfactant were mixed into the
polymer until a very high solids emulsion gel was formed. The
aqueous Makon 10 solution had a viscosity of 5.35 Pa-s at a
shearing gradient of 1 sec.sup.-1 as measured on a Brookefield
viscometer (Brookfield Engineering Laboratories, Inc., Stoughten,
MA. This gel was diluted with 7.08 parts water. This emulsion had
good handling properties and formed a silicone elastomer after
water evaporation. Specifically this dispersion exhibited greater
resistance to extrusion and tooling than a 75% solid silicone
dispersion prepared from a crosslinked silicone emulsion
polymer.
Example 6
Using parts by weight based on siloxane polymer, 100 parts of
50,000 cs (110,000 Mw) --OH endblocked PDMS polymer, 0.8 part
isobutyltrimethoxysilane, and 0.41 part dibutyltindilaurate were
mixed together in a laboratory mixer. 6.00 parts Makon 10 nonionic
surfactant and 3.0 parts water were mixed in until a very high
solids gel emulsion was formed. The aqueous Makon 10 solution had a
viscosity of 5.35 Pa-s at a shearing gradient of 1 sec.sup.-1 as
measured on a Brookefield viscometer (Brookfield Engineering
Laboratories, Inc., Stoughten, Mass. This emulsion had good
handling properties and dried to a silicone elastomer after water
evaporation. Specifically this dispersion exhibited greater
resistance to extrusion and tooling than a 75% solids silicone
dispersion prepared from a crosslinked silicone emulsion
polymer.
Example 7
Using parts by weight based on siloxane polymer, 100 parts of
50,000 cs (110,000 Mw) --OH endblocked PDMS polymer, 0.8 part
isobutyltrimethoxysilane, and 0.41 part dibutyltindilaurate were
mixed together in a laboratory mixer. 6.00 parts Makon 10 nonionic
surfactant and 3.0 parts water were mixed in until a very high
solids gel emulsion was formed. The aqueous Makon 10 solution had a
viscosity of 5.35 Pa-s at a shearing gradient of 1 sec.sup.-1 as
measured on a Brookefield viscometer (Brookfield Engineering
Laboratories, Inc., Stoughten, Mass. The gel was diluted with 20.87
pts of water to yield an 80% silicone solids dispersion. This
emulsion had good handling properties and dried to a silicone
elastomer after water evaporation. Specifically, this dispersion
exhibited greater resistance to extrusion and tooling than a
crosslinked 75% solids silicone dispersion prepared from a
crosslinked silicone emulsion polymer.
Example 8
Using parts by weight based on siloxane polymer solids 100 parts of
the following silanol endblocked PDMS polymers were used
individually to prepare sealant formulations: Huls PS344.5 (8000
cs, 58,000 Mw), Huls PS345.5 (18,000 cs, 77,000 Mw), Huls PS347.5
(50,000 cs, 110,000 Mw), Huls PS348.7 (125,000-175,000 cs, 150,000
Mw). 0.8 parts of isobutyltrimethoxysilane was added to the polymer
and mixed in a laboratory mixer (Whip mix). 4.0 parts of Tergitol
TMN-6 nonionic surfactant and 3.0 parts of water were mixed with
the polymer until a clear gel emulsion was formed. This emulsion
was diluted with 17.1 parts water. Dibutyltindilaurate was added at
a level of 0.4 parts to the emulsion to effect crosslinking of the
emulsion particles. All the emulsions had good handling properties
and dried to a silicone elastomer after water evaporation.
Specifically, these dispersions exhibited greater resistance to
extrusion and tooling than a 75% solids silicone dispersion
prepared from a crosslinked silicone emulsion polymer.
Example 9
Using parts by weight based on siloxane polymer, 100 parts of
50,000 cst silanol endblocked PDMS polymer and 4.0 parts of a 45%
aqueous solution of Tergitol TMN-6 were then mixed until a very
high solids emulsion gel was formed. The aqueous Tergitol TMN-6
solution had a viscosity of 0.082 Pa-s at a shearing gradient of 1
sec.sup.-1 as measured on a Brookefield viscometer (Brookfield
Engineering Laboratories, Inc., Stoughten, Mass.). This emulsion
gel was diluted to an 80% silicone solids emulsion 0.5 parts of
dibutyltindilaurate (DBTDL) and 1.0 part of dimethyl-methylhydrogen
copolymer oligomer were mixed into the emulsion.
This formulation formed a tack free silicone elastomer after water
evaporation. It had a tensile strength of 40 psi and an elongation
of 922 and a Shore A durometer of 13.
Example 10
Using parts by weight based on siloxane polymer, 100 parts of
50,000 cst silanol endblocked PDMS polymer and 4.0 parts of a 45%
aqueous solution of Tergitol TMN-6 were mixed until a very high
solids emulsion gel was formed. The aqueous Tergitol TMN-6 solution
had a viscosity of 0.082 Pa-s at a shearing gradient of 1
sec.sup.-1 as measured on a Brookefield viscometer (Brookfield
Engineering Laboratories, Inc., Stoughten, Mass.). This emulsion
gel was diluted to an 80% silicone solids emulsion. 0.5 parts of
diethylhydroxylamine and 1.0 part of dimethyl-methylhydrogen
copolymer oligomer were mixed into the emulsion.
This formulation, was extruded after 3 days gestation, and formed a
tacky silicone elastomer after standard curing conditions. It had a
tensile strength of 10 psi and an elongation of 2203. The elastomer
was too soft for a Shore A durometer measurement.
Example 11
Using parts by weight based on siloxane polymer, 100 parts of
50,000 cst silanol endblocked PDMS polymer and 4.0 parts of a 45%
aqueous solution of Tergitol TMN-6 were mixed until a very high
solids emulsion gel was formed. The aqueous Tergitol TMN-6 solution
had a viscosity of 0.082 Pa-s at a shearing gradient of 1
sec-.sup.1 as measured on a Brookefield viscometer (Brookfield
Engineering Laboratories, Inc., Stoughten, Mass.). This emulsion
gel was diluted to an 80% silicone solids emulsion. 0.5 parts of
dibutyltindilaurate (DBTDL) and 1.0 part of
vinyltris(methylethylketoxime)silane were mixed into the
emulsion.
This formulation formed a tack free silicone elastomer after water
evaporation. It had a tensile strength of 33 psi and an elongation
of 976 and a Shore A durometer of 3. These films were cast in
accord with the preamble of the example section.
Example 12
Using parts based on siloxane polymer, 100 parts of 60,000 cst
trimethoxysilyl-endblocked PDMS polymer and 4.0 parts of a 45%
aqueous solution of Tergitol TMN-6 were mixed until a very high
solids emulsion gel was formed. The aqueous Tergitol TMN-6 solution
had a viscosity of 0.082 Pa-s at a shearing gradient of 1
sec.sup.-1 as measured on a Brookefield viscometer (Brookfield
Engineering Laboratories, Inc, Stoughten, Mass.). This emulsion gel
was diluted to an 80% silicone solids emulsion. 0.5 parts of TYZOR
DC (a chelated titanate from DuPont, Wilmington, Del.) were mixed
into the emulsion.
This formulation formed a tack free silicone elastomer after water
evaporation. It had a tensile strength of 44 psi and an elongation
of 583 and a Shore A durometer of 6.
Example 13
Using parts by weight based on siloxane polymer, 100 parts of
50,000 cst silanol endblocked PDMS polymer and 4.0 parts of a 45%
aqueous solution of Tergitol TMN-6 were mixed until a very high
solids emulsion gel was formed. The aqueous Tergitol TMN-6 solution
had a viscosity of 0.082 Pa-s at a shearing gradient of 1
sec.sup.-1 as measured on a Brookefield viscometer (Brookfield
Engineering Laboratories, Inc., Stoughten, Mass.). This emulsion
gel was diluted to an 80% silicone solids emulsion 0.5 parts of
dibutyltindilaurate (DBTDL) and 1.0 part of methyltriacetoxysilane
were mixed into the emulsion.
This formulation formed a tack free silicone elastomer after water
evaporation. It had a tensile strength of 77 psi and an elongation
of 1042 and a Shore A durometer of 6.
Example 14
Using parts by weight based on siloxane polymer, 100 parts of
50,000 cst silanol endblocked PDMS polymer and 4.0 parts of a 45%
aqueous solution of Tergitol TMN-6 were mixed until a very high
solids emulsion gel was formed. The aqueous Tergitol TMN-6 solution
had a viscosity of 0.082 Pa-s at a shearing gradient of 1
sec.sup.-1 as measured on a Brookefield viscometer (Brookfield
Engineering Laboratories, Inc., Stoughten, Mass.). This emulsion
gel was diluted to an 80% silicone solids emulsion. 0.5 parts of
dibutyltindilaurate (DBTDL) and 1.0 part of
vinyltriisopropenoxysilane were mixed into the emulsion.
This formulation formed a tack free silicone elastomer after water
evaporation. It had a tensile strength of 48 psi and an elongation
of 553 and a Shore A durometer of 10.
Example 15
Using parts by weight based on siloxane polymer, 100 parts of
50,000 cst silanol endblocked PDMS polymer and 4.0 parts of a 45%
aqueous solution of Tergitol TMN-6 were mixed until a very high
solids emulsion gel was formed. The aqueous Tergitol TMN-6 solution
had a viscosity of 0.082 Pa-s at a shearing gradient of 1
sec.sup.-1 as measured on a Brookefield viscometer (Brookfield
Engineering Laboratories, Inc., Stoughten, Mass.). This emulsion
gel was diluted to an 80% silicone solids emulsion. 0.5 parts of
dibutyltindilaurate (DBTDL) and 1.0 part of
tris(dimethylamino)methylsilane were mixed into the emulsion.
This formulation formed a tack free silicone elastomer after water
evaporation. It had a tensile strength of 37 psi and an elongation
of 874 and a Shore A durometer of 5.
Example 16
Emulsion A:
Using parts weight by weight based on siloxane polymer, in a
laboratory mixer (Hauschild), 0.3 parts of a
platinum/vinylterminated siloxane complex (containing ca. 0.6%
platinum) were mixed into 100 parts of a 55,000 cst Vi terminated
PDMS containing 0.088 vinyl functionality. 4 parts of a 45% solids
aqueous solution of Tergitol TMN-6 were then mixed in until a 94%
silicone solids, oil in water, emulsion gel was formed. This
emulsion gel was diluted to an 80% silicone solids emulsion. The
aqueous Tergitol TMN-6 solution had a viscosity of 0.082 Pa-s at a
shearing gradient of 1 sec.sup.-1 as measured on a Brookefield
viscometer (Brookfield Engineering Laboratories, Inc, Stoughten,
Mass.).
Emulsion B:
Using parts by weight based on siloxane polymer, in a laboratory
mixer (Hauschild), 1.5 parts of dimethyl-methylhydrogen siloxane (5
cst viscosity, containing 0.76% Si--H) were mixed into 100 parts of
a 55,000 cst vinyl terminated PDMS containing 0.088 vinyl
functionality 4 parts of a 45% solids aqueous solution of Tergitol
TMN-6 were then mixed in until a 94% silicone solids, oil in water,
emulsion gel was formed. This emulsion gel was diluted to an 80%
silicone solids emulsion. The aqueous Tergitol TMN-6 solution had a
viscosity of 0.082 Pa-s at a shearing gradient of 1 sec.sup.-1 as
measured on a Brookefield viscometer (Brookfield Engineering
Laboratories, Inc., Stoughten, Mass.).
Emulsion C:
Equal parts of Emulsion A and Emulsion B were mixed in a laboratory
mixer (Hauschild).
Emulsion C, after 4 days, formed a tack free silicone elastomer
after water evaporation.
Example 17
Using parts based on siloxane polymer, 100 parts of 60,000 cst
trimethoxysilyl-endblocked PDMS polymer and 4.0 parts of a 45%
aqueous solution of Tergitol TMN-6 were mixed until a very high
solids emulsion gel was formed. The aqueous Tergitol TMN-6 solution
had a viscosity of 0.082 Pa-s at a shearing gradient of 1
sec.sup.-1 as measured on a Brookefield viscometer (Brookfield
Engineering Laboratories, Inc., Stoughten, Mass.). This emulsion
gel was diluted to an 80% silicone solids emulsion. 0.54 parts of
hexylamine and 0.72 parts of octanoic acid were mixed into the
emulsion.
This formulation formed a tack free silicone elastomer after water
evaporation.
Example 18
Using parts based on siloxane polymer, 100 parts of 50,000 cst
silanol-endblocked PDMS polymer and 4.0 parts of a 45% aqueous
solution of Tergitol TMN-6 were mixed until a very high solids
emulsion gel was formed. The aqueous Tergitol TMN-6 solution had a
viscosity of 0.0082 Pa-s at a shearing gradient of 1 sec.sup.-1 as
measured on a Brookefield viscometer (Brookfield Engineering
Laboratories, Inc., Stoughten, Mass.). This emulsion gel was
diluted to an 81% silicone solids emulsion. 0.2 parts of stannous
octoate and 2.00 parts of 50% solution of vinytrimethoxysilane in
pH 4 water(prehydrolyzed vinyltrimethoxysilane) were mixed into the
emulsion.
This formulation formed a tack free silicone elastomer after water
evaporation. The tensile was 84 psi, the elongation was 1733 and
the Shore A durometer was 2.
* * * * *